AAT ICAS 0600 ✧ transitional specifications

this document describes AAT ICAS transitional specifications. please refer to AAT ICAS 1002 for access to information about the most recent version activity that may pertain to transitional specifications.

• purpose of transitional specifications
• rationale for transitional specifications
• specification of transitional standards
• specification of transitional and RESTRICTED standards
• rationale for specification of transitional standards
• 0600-ps01 review of specification of metric reference units
• 0600-ps02 review of specification of principles of coherence
• 0600-ps03 review of case structure of metric prefixes
• 0600-ps04 review of usage guidelines for metric terms for numerical reference
• 0600-ps05 review of name and symbol for reference unit of mass
• 0600-ps06 review of name and symbol for reference unit of thermodynamic temperature
• 0600-ps07 review of metric prefix names and symbols for IDC main unit and submultiples
• 0600-ps08 review of transitional hyphenation guideline
• 0600-ps09 review of ICAS time-derived units
• 0600-ps10 general review of ICAS element sets and standards
• 0600-ps11 general review of ICAS provisions for customary use
• 0600-ps12 general review of coordinating prefix expressions
• 0600-ps13 general review of new leap year rules
• general review of leap day algorithms
• specification of metric reference units
• table 0600.1 ✧ AAT ICAS transitional set of metric reference units
• Appendix A—some initiatives for metric timekeeping or calendaring
• Appendix B—some normative references

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purpose of transitional specifications

ICAS is developed toward the specification of a coherent system of metric units that can accommodate conventional use of uniform scales of calendar and clock. as such the development of ICAS should also be considered as subject to future review by standards authorities for purposes of coordination with the International System of Units (SI) and other standards.

AAT ICAS has pursued the development of uniform scales of calendar and clock with a goal of determining a more metric interface for more measures of time. some of the ICAS specifications integrate metric specifications from SI. however ICAS project developments have also found certain plausible methods for integrating metric specifications for a possible future version of SI.

the purpose of these transitional specifications is to facilitate a transitional coordination of SI and ICAS in support of a continuing development and use of a coherent metric system of measurement that is suitable 'for all people, for all time'.

toward development of a more integrated metrological framework; revisions to ICAS should particularly review approaches proposed for the redefinition of SI units such as the kilogram, ampere, kelvin, and mole. [1,2,5] specifically, some widely accepted criteria for the formulation of definitions for metrological units [1] are considered:

• (1)—continuity between the realizations of the old and the new definition,
• (2)—realization of the unit with a smaller (or at least the same) measurement uncertainty as before,
• (3)—better stability of the quantity concerned,
• (4)—consistency and coherence with the other SI base units,
• (5)—possibility of realization anywhere and at any time, at least in principle,
• (6)—based on commonly accepted laws in physics,
• (7)—conceptually clear and easy to understand.

yet certain criteria for the development of definitions for future metrological or 'metric' units might be reconsidered or revised to encompass one or more SI and ICAS frameworks as follows:

• (1)—referential equivalence or natural invariance in the practical realization of a unit,
• (4)—consistency and coherence with a larger number of metrological reference units,

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rationale for transitional specifications

with reference to the 8th edition of the SI Brochure, 2006 March; AAT ICAS would like to suggest a review of guidelines for the formatting of metrological information. this review might encompass the 'rules for writing' style guidelines, the formulation of XML (eXtensible Markup Language) or CSS (Cascading Style Sheets) style resources for preparing metrological information, or a specification of standard terms with reference to international and local usage practices. such a review provides an opportunity to harmonize the metric style guidelines used among scientific and technical disciplines with those style guidelines used among the general media.

moreover, a review of the specification of metrological 'formatting' in the definition of the SI unit of time offers an opportunity to address improvements in the formatting of date and time information.

one approach that is already part of the present SI is to define a unit of time as a duration of a standard modulation of the periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.

in the case of the SI second, the standard modulation is defined as a caesium 133 frequency of 9 192 631 770 atomic periods. with reference to Guinot (Metrologia 34.3, p.289), the SI second relates to the UT1 length of the day LOD by the following factor: 1 LOD = 86400 s. the LOD relates to the ICAS (Integrated Chronological Applications System) chron (Xn) as equivalent in magnitude.

in the case of the LOD, a standard modulation may be defined as a practical LOD submultiple such as 1 x 10^-5, as in the case of the ICAS tikochron (tiXn), as a caesium 133 frequency of 7 942 433 849.3 atomic periods. the magnitude of the ICAS tikochron relates to the SI second by the following exact factor: 1 tiXn = 0.864 s.

alternatively a LOD submultiple of 1 x 10^-4, as in the case of the ICAS tokochron (toXn), would be defined as a caesium 133 frequency of 79 424 338 493 atomic periods. the magnitude of the ICAS tokochron relates to the SI second by the following exact factor: 1 toXn = 8.64 s.

regardless of the frequency modulation that one applies, timepoints can be specified by which synchronizations between instruments can be compared (such as midnight or noon UT). such an approach might accommodate improvements in the reformulation of references to metrological [proper with reference to space-time relativity] units for ubiquitous date and time expressions in terms of timepoints formatted by calendar, by LOD decimal clock, or by 24/60/60 customary clock.

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specification of transitional standards

AAT ICAS proceeds with the specification of ICAS transitional standards of metric measure for those AAT ICAS specifications that are not yet summarized by SI, and for which an ICAS transitional specification is not deemed by AAT ICAS to require a respecification of existing SI standards. an AAT review of those transitional standards relating directly to the development and use of uniform scales of calendar and clock has determined that ICAS approaches can accommodate a coordination of both SI and ICAS.

an AAT ICAS review of those transitional standards concerning customary scales of calendar and clock (the Gregorian calendar, the clock dial of 24 hours of 60 minutes and 60 seconds, and so forth) has deemed that ICAS standards do not require a respecification of customary scales of calendar and clock.

to any extent that ICAS or other standards are developed or respecified, AAT shall further make efforts to develop and represent standards systems with a provision for the preservation of current or previous standards systems. some of the ways in which this provision is accomplished is by the review, catalog, development, or integration of a variety of standards resources references.

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specification of transitional and RESTRICTED standards

for those ICAS transitional standards that are deemed by AAT ICAS to potentially affect a particular specification of a current or future SI standard, AAT ICAS shall make efforts to designate such standards for any instance of specification as transitional and RESTRICTED. standards that are transitional and RESTRICTED are intended strictly for purposes of review and are not authorized for development nor for use by any parties without express permission.

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rationale for specification of transitional standards

transitional specifications are developed and reviewed primarily for cases that are deemed by AAT ICAS to not require a respecification of standards other than ICAS. however for cases that might involve a current or future respecification of another standard, AAT shall consider provisions for minimizing the effects of conformance with any respecification, and for reviewing possible pre- and post-transitional provisions.

an AAT review of metric principles of style in terms of user-centered design suggests the following transitional or transitional and RESTRICTED specifications:

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0600-ps01 review of specification of metric reference units

status note: this section 0600-ps01 is designated by AAT ICAS as a transitional and RESTRICTED specification. this material is intended strictly for purposes of review and is not authorized for development nor for use by any parties without express permission. material is subject to change during a process of review, and any citation of this section or material must note the status in effect.

transitional specifications for integrating ICAS principles for specifying a principle class of reference units are designated in anticipation of a possible transition to a future metric system integrating SI and ICAS approaches.

specification of a class of reference units would serve the purpose of determining a possible future set of metric units similar to the present class of SI base units, yet integrating transitional ICAS specifications.

a metrological foundation for the specification of metric reference units is appropriated from certain principles of coherence specified in SI and ICAS; however descriptions of these principles can be subject to different technical labels. principles of constancy and reproducibility also extend to a consideration of a class of metric reference units.

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0600-ps02 review of specification of principles of coherence

status note: this section 0600-ps02 is designated by AAT ICAS as a transitional specification. material is subject to change during a process of review, and any citation of this section or material must note the status in effect.

transitional specifications for the description of metrological principles of coherence are designated for ICAS; however descriptions of these principles can be subject to different technical labels in SI.

coherence—generally, a principle or quality of a measure that may concern the unitary, decimal, mathematical, referential, or terminological nature of a unit system. see also terms 'metric' and 'uniform' in AAT ICAS 3105.

decimal coherence—a principle or quality by which a system of units is mathematically related by no factors other than 10 raised to the power of a positive or negative integer.

mathematical coherence—a principle or quality by which a particular system of units accommodates a coherent system of numerical or algebraic representation.

metrological coherence—the level of extent to which a particular set of metric units accommodates principles of unitary, decimal, mathematical, referential, and terminological coherence.

referential coherence—a principle or quality by which a particular unit is designated as a metric unit to accommodate practical use in terms of principles of constancy, reproducibility, and uniformity. also concerns the determination of a unit in terms of a fixed or coordinated measure.

semi-coherence—a principle or quality by which a particular system of units is related by principles of accommodating uniformity and limiting exception to uniformity, especially in comparison with other principles of coherence.

terminological coherence—a principle or quality by which a particular system of units is organized into distinct schemes for the practical expression of names and symbols for purposes of accommodating clear and concise communication of qualitative and quantitative information about particular units.

unitary coherence—a principle or quality by which the particular units in a system or set are related to other particular units by the rules of multiplication and division with no numerical factor other than the number 1 ever occurring in the expressions for the particular units in terms of the particular reference units.

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0600-ps03 review of case structure of metric prefixes

status note: this section 0600-ps03 is designated by AAT ICAS as a transitional and RESTRICTED specification. this material is intended strictly for purposes of review and is not authorized for development nor for use by any parties without express permission. material is subject to change during a process of review, and any citation of this section or material must note the status in effect.

transitional specifications for integrating ICAS principles of case-structure anticipate a future specification of standard metric prefix symbols that, in a context of international or local use, are the same for any language. because the metric prefixes are intended for schematic use with any of the metric reference units, and also for common international or local use; AAT concludes that the standardized designation of a system of prefix names and symbols imposes a stronger need for limiting exception than for the accommodation of the names or symbols of any of the particular reference units.

whereas a recent SI specification of the metric prefix symbol for the decimal multiple of 1000 consists of a lower-cased letter 'k', and whereas the case structure of this prefix symbol has formerly been an exception for a schematic rule of the use of upper-cased letters for decimal multiple prefixes, and whereas the case structure of prefix symbols for all decimal submultiples (or decimal multiples less than one) is lower-cased; AAT designates an ICAS specification for a respecification of the symbol for unit multiple of 1000 in terms of an upper-cased letter 'K' as transitional and RESTRICTED.

although the symbols for hecto (100) and deca (10) are also recently specified as lower-cased 'h' and 'da' expressions; this transitional and RESTRICTED specification would also concern a respecification of the casing of the prefix symbol for hecto as an upper-cased 'H', and a respecification of the casing of the prefix symbol for deca as an upper-cased 'D'.

a respecification would not affect the name of the metric prefix 'kilo' that is already widely used (nor the names of the less widely used prefixes for 'hecto' and 'deca'). certain common usages of the symbol for the prefix 'kilo', especially for expressions of indefinite reference, are already commonly expressed in upper-case. if the transitional specification were accommodated, a usage guideline would more consistently reflect the use of upper-cased prefix symbols for decimal multiples, and the use of lower-cased prefix symbols for decimal submultiples. specification could serve the expression of decimal multiples and submultiples for all metric reference units with no exceptions to a common scheme for a case-structure reference unit expression. respecification could also facilitate an improvement in ways that metric usage guidelines could be learned and used.

transitional provisions for a respecification might encompass recommendations for the declaration of designated style notes for the expression of metric prefixes in pre- and post-transitional documents.

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0600-ps04 review of usage guidelines for metric terms for numerical reference

status note: this section 0600-ps04 is designated by AAT ICAS as a transitional specification. material is subject to change during a process of review, and any citation of this section or material must note the status in effect.

transitional specifications for integrating ICAS principles for usage of expressions of indefinite reference anticipate a possible transition to a future metric system integrating SI and ICAS, and also anticipate a possible transition to a future language usage styleguide integrating ICAS and other language usage guidelines.

whereas metric prefixes recently specified in SI can accommodate the practicable expression of certain common unit quantities in terms of an established common set of decimal multiples and submultiples; and whereas other customary terms for expressing numerical values may be subject to different customary meanings in different regions; AAT designates an ICAS specification for the appropriation of metric prefixes for indefinite reference as transitional.

an ICAS specification of an indefinite reference expression designates the use of metric prefixes for other non-scalar practical quantities not otherwise designated as metric units, as expressions of indefinite reference; especially for the purpose of designating an alternative to the use of customary terms such as 'million' and 'billion' that may have different customary meanings in different regions. examples of practical quantities include monetary reference expressions (megadollars, megafrancs, megapounds, and so forth.); web site visitors or hits (kilovisits, megahits, and so forth.); and so forth.

for purposes of expressing quantities in terms of indefinite reference, one should select appropriate expressions that are practicably referential in nature, that are relatively coherent, and that can be expressed with decimals without requiring cumbersome conversions from non-decimal fractions. for example, one might choose 'megadollars' or 'megacoins' as an indefinite reference expression in place of 'megapennies', 'meganickels', or 'megadimes'. please note that minutes, hours, and days are excluded from decimal-prefix expression as indefinite reference by both SI and ICAS. expressions of the SI scalar magnitude for time (second) are specified in SI. expressions of the ICAS scalar magnitude for time (chron) are specified in ICAS.

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0600-ps05 review of name and symbol for reference unit of mass

status note: this section 0600-ps05 is designated by AAT ICAS as a transitional and RESTRICTED specification. this material is intended strictly for purposes of review and is not authorized for development nor for use by any parties without express permission. material is subject to change during a process of review, and any citation of this section or material must note the status in effect.

transitional specifications for integrating ICAS principles for the naming and expression of particular reference units anticipate a possible transition to a future metric system integrating SI and ICAS.

whereas a recent version of SI accommodates an exception for the name of the reference unit of mass (for historical reasons in lieu of conformance with other reference units), named 'kilogram' and expressed symbolically as 'kg', to include a prefix. and whereas the lower case letter 'k' is the only exception to a scheme of upper-cased prefixes for reference unit multiples; AAT designates an ICAS specification for a respecification of the reference unit of mass name to 'onc', and symbol to 'o' as transitional and RESTRICTED.

a respecification would not affect the quantitative value definition of the reference unit of mass. the transitional name is determined by AAT to be plausibly distinguishable from the present name, and from the names of other metrological units. the expression of decimal multiples and submultiples for the transitional unit of mass would conform with the rules for the other units. the unit name 'kilogram' would be replaced by 'onc', and unit symbol 'kg' would be replaced by 'o'. the unit name 'gram' would be replaced by 'millionc'; and unit symbol 'g' would be replaced by 'mo'. it may be that a respecification could facilitate some improvement in ways that metric usage guidelines could be learned and used. yet AAT has not reviewed ways that respecification might affect the formulation of the units derived in terms of the unit of mass, nor has AAT considered the implications of an alternative respecification of the present unit of 'gram' as a possible reference unit.

transitional provisions for a respecification might encompass recommendations for the declaration of the name, symbol, and reference definition of any mass units used in pre- and post-transitional documents. other transitional provisions might encompass recommendations for the declaration of designated style notes for the expression of mass unit references in pre- and post-transitional documents.

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0600-ps06 review of name and symbol for reference unit of thermodynamic temperature

status note: this section 0600-ps06 is designated by AAT ICAS as a transitional and RESTRICTED specification. this material is intended strictly for purposes of review and is not authorized for development nor for use by any parties without express permission. material is subject to change during a process of review, and any citation of this section or material must note the status in effect.

transitional specifications for integrating ICAS principles for the naming and expression of particular reference units anticipate a possible transition to a future metric system integrating SI and ICAS.

whereas a recent version of SI specifies a symbol for the unit of thermodynamic temperature that might possibly be appropriated for other schematic use; and whereas the name of the unit of thermodynamic temperature 'Kelvin' is named for William Thomson, Lord and Baron Kelvin of Larg; AAT designates an ICAS specification for the respecification of the reference unit of thermodynamic temperature name to a transitional name possessing an initial letter 'b', and symbol to 'b' as transitional and RESTRICTED.

although there is presently no rigorous reason to rename a unit or unit symbol just because of a similarity to a prefix symbol; given the very widespread use of SI, some additional consideration of the schematic principles for writing metric units may help to inform initiatives for deriving names and symbols of possible future units.

AAT further considers that a respecification of the name of the reference unit of thermodynamic temperature may be appropriated from the proper name of a place or body of water. a brief list of names that might plausibly accommodate a respecification might include, yet would not be limited to the following: 'baron', 'baden', 'barrow', 'bath', 'bay', or 'boulder'. AAT may elect to not further specify any transitional respecifications of the name for the reference unit of thermodynamic temperature.

a respecification would not affect the magnitude or dimension of the definition of the reference unit of thermodynamic temperature. a respecification of the name of the reference unit of thermodynamic temperature would also not affect the name or symbol of the unit for Celsius temperature. the transitional name and symbol would be reviewed on the basis of being plausibly distinguishable from the names and symbols of other particular units, and would moreover be reviewed on the basis of being a plausible accommodation for a metric unit name and symbol. it may be that a respecification could accommodate other transitional respecifications determined to impose a greater need for schematic use.

transitional provisions for a respecification might encompass recommendations for the declaration of the name, symbol, and reference definition of any thermodynamic temperature units used in pre- and post-transitional documents. other transitional provisions might encompass recommendations for the declaration of designated style notes for the expression of thermodynamic temperature unit references in pre- and post-transitional documents.

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0600-ps07 review of metric prefix names and symbols for IDC main unit and submultiples

status note: this section 0600-ps07 is designated by AAT ICAS as a transitional specification. material is subject to change during a process of review, and any citation of this section or material must note the status in effect.

transitional specifications for integrating ICAS principles for the designation of metric prefix names and symbols for IDC unit submultiples anticipate a possible transition to a future metric system integrating SI and ICAS.

whereas a recent version of SI specifies of a reference unit for time that is not decimally coherent with a uniform measure of a main unit of 1 day; AAT concludes that a reference unit for time formulated in terms of uniform measure of a main unit of one day could plausibly be specified as in ICAS specifications. AAT moreover concludes that metric prefixes could appropriately be specified for the nearest main unit decimal approximations of the SI second.

ICAS specifies the transitional designation of the prefixes for reference unit submultiple 10-4 name 'toko' and symbol 'to', and for reference unit submultiple 10-5 name 'tiko' and symbol 'ti'. the transitional specifications are determined by AAT to facilitate increased precision and calculability that is accommodated by a decimalized scale of time.

an AAT review of ICAS has determined that IDC specifications of a main unit of time do not affect the name, symbol, or magnitude of the SI unit for time (second), and thus do not necessitate a respecification of the SI second. the ICAS name and symbol for the IDC main unit chron (Xn) is derived from a Greek term root expression corresponding to general expressions of time.

an AAT review of ICAS has determined that IDC specifications of main unit submultiples do not affect the name or symbol of other metric prefixes specified in SI, and thus do not necessitate a respecification of the other prefix multiples or submultiples currently specified in SI. the ICAS name and symbol for submultiple unit names 'tik' and 'tok' are derived from term root expressions that are etymologically common to a number of western languages, and that moreover generally correspond to abstract expressions of immediate time.

speed of light is a physical constant whether measured in terms of a second or in terms of a tikochron. for the purposes of defining a fixed measure for a tikochron that can also accommodate the formulation of a coherent set of reference units; the length of the metre is also fixed as a metrological constant.

the length of a metre, defined in SI-1998 as the length of path travelled by light in vacuum during a time interval of 1/299 792 458 of a second, is thus equivalent to the same path length during the same interval measured in terms of 1/346 982 011.6 of a tikochron (or more preferably 1/3 469 820 116 of a microchron).

a measure of the speed of light fixed at exactly 299 792 458 m·s-1 is similarly thus equivalent to a measure of the speed of light fixed at exactly 259 020 683.71 m·tiXn-1 (or for a whole number 25 902 068 371 m·mXn-1).

transitional provisions for this specification might encompass recommendations for the declaration of the name, symbol, and reference definition of any metric time units or prefixes used in pre- and post-transitional documents. additional transitional provisions related to the development of an infrastructure for the use of uniform scales of calendar and clock may also be appropriate.

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0600-ps08 review of transitional hyphenation guideline

status note: this section 0600-ps08 is designated by AAT ICAS as a transitional and RESTRICTED specification. this material is intended strictly for purposes of review and is not authorized for development nor for use by any parties without express permission. material is subject to change during a process of review, and any citation of this section or material must note the status in effect.

As a transitional usage guideline to facilitate the practicable expression of symbolic expressions of metric reference units for the transitional specification of unit submultiples, AAT designates the following hyphen rule as transitional and RESTRICTED:

transitional prefix expressions are used without hyphens in cases where the lower-cased expression of the prefix is used with an upper-cased reference unit term. transitional prefix expressions are however expressed with a hyphen when used with other lower-cased reference units. consider the use of uncoordinated or non-transitional expressions in cases where the use of coordinated or transitional expressions would otherwise be cumbersome.

an AAT review has determined that this issue concerns the plausible use of a coordinated prefix unit with a present standard lower-cased unit multiple that can be expected to be plausible for calendrical use (or potentially other plausible uses). this guideline would be formulated to accommodate the present exception to the case structure of upper-cased symbols for decimal unit multiples. a respecification of the case structure for metric prefixes per the provision specified in 0600-ps03 would make 0600-ps08 unecessary, and would further corroborate improvements in the ways that metric usage guidelines could be learned and used.

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0600-ps09 review of ICAS time-derived units

status note: this section 0600-ps09 is designated by AAT ICAS as a transitional specification. material is subject to change during a process of review, and any citation of this section or material must note the status in effect.

transitional specifications for integrating ICAS principles for the designation of metric unit names and symbols for units derived in terms of IDC specifications anticipate a possible transition to a future metric system integrating SI and ICAS.

specifications for time-derived units in SI, such as units from table 3 of the 1998 SI brochure, extend to the formulation of a set of time-derived units for IDC that are for each case related by a fixed time factor constant to the set of time-derived units in SI.

an AAT review of ICAS has determined that IDC specifications of time-derived units do not affect the name, symbol, or magnitude of time-derived units specified by SI, and thus do not necessitate a respecification of the definitions for the units. the names and symbols formulated for the ICAS set of time-derived units were derived from latin root terms for a group of monocot and dicot plant family names. each formulated unit name is lowercased and each symbol consists of two lower-cased letters.

transitional provisions for this specification might encompass recommendations for the declaration of the name, symbol, and reference definition of any metric time units used in pre- and post-transitional documents. additional transitional provisions related to the development of an infrastructure for the use of uniform scales of calendar and clock may also be appropriate.

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0600-ps10 general review of ICAS element sets and standards

status note: this section 0600-ps10 is designated by AAT ICAS as a transitional specification. material is subject to change during a process of review, and any citation of this section or material must note the status in effect.

transitional specifications for integrating ICAS principles for the designation of metric unit names and symbols for elements formulated for IDC specifications anticipate a possible transition to a future metric system integrating SI and ICAS.

an AAT review of ICAS element sets may concern the present AAT ICAS English language specifications or may concern the development of additional localizations. AAT shall review comments about ICAS standards on an ongoing basis.

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0600-ps11 general review of ICAS provisions for customary use

status note: this section 0600-ps11 is designated by AAT ICAS as a transitional specification. material is subject to change during a process of review, and any citation of this section or material must note the status in effect.

transitional specifications for integrating ICAS principles for accommodating uses of customary systems of measure anticipate a continuing development and accommodation of a possible future system of measurement that is suitable 'for all people, for all time'.

systems and uses of measure, both metric and customary, are to certain extents accommodated by and are to certain extents accommodating of a variety of economic infrastructures and practices.

an AAT review of ICAS provisions for customary use supports efforts to respect the use of customary scales of measure in promoting support for metrication.

the use of best practices is encouraged whenever possible. the provision of future practices should take into account principles and practices for improving the accommodations of a system, infrastructure, or practice.

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0600-ps12 general review of coordinating prefix expressions

status note: this section 0600-ps12 is designated by AAT ICAS as a transitional specification. material is subject to change during a process of review, and any citation of this section or material must note the status in effect.

this provision also concerns issues presented in the transitional and RESTRICTED specification 0600-ps08. please also refer to AAT ICAS 2021 for usage guidelines relating to coordinating prefixes 'ten', 'hun', and 'pre'.

the practical use of prefixes stepped in thousands from a reference unit (for example, micro, milli, kilo, Mega, and so forth.) can accommodate an easier process of metrication due to easier calculability for more types of uses. yet the fact that the remaining prefixes (centi, deci, deka, and hecto) are not stepped by a thousand from a reference unit does not mean that they are not practical. and apart from fixed-measures of time determined in terms of tikochron or tokochron approximations of the fixed-second, the practical measure of coordinated durations of time may benefit from the practicality of references to ubiquitous instances of 'tik' or 'tok'. the superior precision of a completely decimal time interface in comparison with a fraction-constrained interface can also benefit the measurement of time for both fixed and coordinated uses. for these reasons, provisions for developing usage guidelines for each type of prefix (thousand, non-thousand, and coordinating) are under review.

an AAT review has determined that this issue concerns the plausible use of coordinated prefix units that can be expected to be plausible for calendrical use (or potentially other plausible uses). additional review of element set structuring remains in process.

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0600-ps13 general review of new leap year rules

during development of the new CHARTdateEPOCH calendar spreadsheet, which is an 'ICAS-in-use' open-source document, a 4000-year rule, and a 900-year rule (see Calendar FAQ at www.tondering.dk) were considered.

AAT ICAS decided not to specify any additional leap year rules for ICAS at this time for the following reasons:

a 4000-year rule of 969 (rather than 970) leap days in 4000 years for the Gregorian calendar has not yet gathered official consensus. (and a similar 900-year rule of 218 leap days in 900 years from the 1920s will not conflict with the Gregorian calendar until AD 2800.)

as all of the ICAS Uniform Calendar (UC), New Calendar (NC), and New Calendar Day Notation (NDN) specifications are at present specified to observe the same durations of calendar year that are used by the Gregorian calendar; the present rule4n100 and rule400 provide the most uniform rules for use with the present Gregorian calendar.

the use of a common day-of-year table among the Uniform and Gregorian calendars simplifies calculations.

it is simpler to determine an NDN number from a Gregorian calendar date when both the UC and the G calendar scales use the same leap year rules.

to retain a similar uniformity with a scale using different leap-year rules, a new scale of day notation might be suggested. such a scale might be subject to a correction of 3 days at NC 12000 for the rule4000 or 4 days at NC 12000 for the 900rule218.

should a 4000-year rule be discussed, AAT ICAS would recommend that no rule be established that would affect any of the years by which the Julian or the Gregorian calendars have been actively observed. this includes the years between the transition from BC to AD through AD 2000.

that leaves candidates for rule4K to include AD 2400, AD 2800, AD 3200, or AD 3600. respectively, the above rules would also concern NC 8400, NC 8800, NC 9200, and NC 9800.

if a 4000-year rule is to be adopted, then there is time until NC 12400 (AD 2400) to decide upon the most remaining options for a 4000-year rule.

if a 900-year218 rule is to be adopted with wide consensus, then to retain simplicity it might be more convenient to consider the designation of a future Calendar scale with known offsets to both the Julian and to the Gregorian (and therefore to the BasilicumUC [or bUC]) calendar scales.

in any case, a future ICAS scale of day notation could be generated from a particular future calendar scale.

if the same 'NDN' identifier is designated for use, then wherever necessary a 'bNDN' scale could be distinguished from a 'cNDN' scale.

wherever necessary a 'bUC' scale could be distinguished from a 'cUC' calendar scale.

throughout any of these considerations, a 7-day daygroup period, that is independent of any of the calendar scales, can be defined with reference to any of the calendar scales.

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leap day algorithms

Claus Tondering's document Frequently Asked Questions about Calendars provides a very informative historical overview of many world calendars.

the sections describing when new year's began and when leap days were observed might suggest that it is simpler to make certain calendrical calculations (such as calculating the day of the week, month, or year) if a leap day (intercalated day) is observed at the end of a year.

a leap day at the end of a calendar year was observed in the French Revolutionary Calendar.

a leap day at the end of a calendar year is also observed in the ICAS Uniform Calendar (which observes the same New Year's day, and New Year's Eve, as the Gregorian calendar).

if a leap day is not at the end of a calendar year, then an algorithm to calculate a leap day as if it were at the end of a year can facilitate the use of simpler formulas for various calendrical calculations.

for an example that is also acknowledged to Claus Tondering, please see _XSLT Cookbook_ (2nd Edition) by Sal Mangano. a sidebar on page 115 describes a method for calculating the day of the week given a year, month, and day.

for examples of algorithms for the ICAS Uniform Calendar, please see the AAT ICAS code library, and the AAT ICAS standards documents.

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aatideas.org document updated:

system identifiers		datetime
long	short	scale	value
Uniform Calendar	UC	UCN	12019 S19 Yellow
Inter-Dial Clock	IDC	zone(UT)	t339 tt050
'ICAS in use' can accommodate calendar and clock formatting 'for all people, for all time'.
day of year	D-o-Y	AD common year day	139
Gregorian calendar	G	G	2019 May 19 Sunday
seconds, minutes, hours	SMH	UT	08:08:14
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