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AAT ICAS 1300 ✧ Inter-Dial Clock (IDC) specification

document note: this document is part of the Integrated Chronological Applications System (ICAS). Alliance for the Advancement of Technology (AAT) provides ICAS standards documents subject to terms of use described in document AAT ICAS 9010. please refer to other key AAT ICAS standards documents accessible via the AAT ICAS web site at for important information about ICAS.


general description

Inter-Dial Clock (IDC) methods for the specification of time integrate schemes for the decimal expression of times coherent to a main unit of one day. the IDC scale is designated as a principal ICAS time scale.


specification of main unit

the main unit of the IDC system is derived from a duration of one day in the traditional clock system of 24 hours. time in the IDC system is expressed in terms of a decimal value of the time elapsed from midnight. for example, a local time of noon corresponds to a time value of 0.5 of the IDC main unit. the main unit may be further specified for coordinated or fixed implementations of use.

the coordinated implementation of the main unit is derived from the system of coordinated universal time (UTC) used for civil timekeeping, and is set as the length of one day UTC.

a fixed implementation of the main unit is specified in terms of a subunit-multiple that is derived from the SI second: a duration of "9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom." (SI there are 86 400 seconds in a day of the traditional clock system, and the closest approximation of a second in terms of a coherent decimal unit is a 100 000th of a day. one such decimal subunit of a day (1 x 10-5 main IDC) is equivalent to 0.864 seconds, and a fixed-measure expression of the subunit is equivalent to 7 942 433 849.3 atomic periods per above. alternately a fixed-measure subunit of a 10 000th of a day (1 x 10-4 main IDC) is expressed as equivalent to 79 424 338 493 atomic periods per above. a fixed implementation of the main unit may be derived from fixed-measure subunits.

this specification also provides for the following additional expressions: the natural resonance frequency of the cesium atom is 9 192 631 770 Hz (per SI whereas 1 meter solana (m⋅so) is an alternative representation of equal quantity of 1 meter per tik (m/tiXn), the natural resonance frequency of the cesium atom is 7 942 433 849.3 m⋅so (per ICAS and SI alternatively the natural resonance frequency of the cesium atom can also be expressed as 79 424 338 493 m/toXn (per ICAS and SI

other fixed-measure implementations of the main unit or a subunit thereof may also be designated so long as the fixed-measure is highly approximating a corresponding UTC unit, is sufficiently defined, and is sufficiently specified.

the main unit of the Inter-Dial Clock may be designated in terms of localized term sets (please see AAT ICAS 1400).


specification of time-derived units

specifications for time-derived units in SI, such as units from table 3 of the 1998 SI brochure, the International System of Units (SI), extend to the formulation of a set of time-derived units for IDC that are related by a fixed time factor constant to the set of time-derived units in SI. for purposes of accommodating scalar coherence of scalar unit systems, the different sets of SI and ICAS time-derived units should also not be mixed in uses of time-derived units.


table 1300.1 ✧ ICAS time-derived units

physical quantityname-SIsymbol-SIterms derivedterms basefactor ICASname ICASsymbol ICAS
timesecondss1 tiXn = 0.864 stikochrontiXn
units from table 3 of 1998 SI brochure. ICAS fixed time factor constant (x) = 0.864.
frequencyhertzHzs-11 so = (x) Hzsolanaso
forcenewtonNm ⋅ kg ⋅ s-21 mu = (x-2) Nmusamu
pressure, stresspascalPaN/m-2m-1 ⋅ kg ⋅ s-21 sl = (x-2) Pasalicasl
energy, work,
quantity of heat
jouleJN ⋅ mm2 ⋅ kg ⋅ s-21 ju = (x-2) Jjuncaju
power, radiant fluxwattWJ/sm2 ⋅ kg ⋅ s-31 po = (x-3) Wpoapo
electric charge,
quantity of electricity
coulombCs ⋅ A1 cu = (x) Ccucurbitacu
electric potential difference,
electromotive force
voltVW/Am2 ⋅ kg ⋅ s-3 ⋅ A-11 mv = (x-3) Vmalvamv
capacitancefaradFC/Vm-2 ⋅ kg-1 ⋅ s4 ⋅ A21 fa = (x4) Ffabafa
electric resistanceohmΩV/Am2 ⋅ kg ⋅ s-3 ⋅ A-21 or = (x-3) Ωorchidaor
electric conductancesiemensSA/Vm-2 ⋅ kg-1 ⋅ s3 ⋅ A21 rn = (x3) Sranuncularn
magnetic fluxweberWbV ⋅ sm2 ⋅ kg ⋅ s-2 ⋅ A-11 as = (x-2) Wbasteraas
magnetic flux densityteslaTWb/m2kg ⋅ s-2 ⋅ A-11 la = (x-2) Tlamiala
inductancehenryHWb/Am2 ⋅ kg ⋅ s-2 ⋅ A-21 ro = (x-2) Hrosaro
activity (referred to a nucliotide)bequerelBqs-11 br = (x-1) Bqbromelabr
absorbed dose,
specific energy (imparted)
grayGyJ/kgm2 ⋅ s-21 ir = (x-2) Gyiridair
dose equivalent,
ambient dose equivalent,
directional dose equivalent,
personal dose equivalent,
organ equivalent dose
sievertSvJ/kgm2 ⋅ s-21 am = (x-2) Svamaryllaam


table 1300.2 ✧ ICAS fixed time factor constant

(x)-3≈ 1.55045359574252
(x)-2≈ 1.33959190672154
(x)-1≈ 1.15740740740741
(x)1= 0.864
(x)2= 0.746496
(x)3= 0.644972544
(x)4= 0.557256278016


specification of dial units

an IDC main unit is further specified in terms of a dial unit, which designates how a main unit is divided into smaller units. as in the traditional clock dial, IDC dials are divided into major and minor clock units. major clock units designate a primary subdivision of the main unit. minor clock units designate the subdivision of major clock units. subminor clock units moreover designate the subdivision of minor clock units.

particular clock units for an IDC dial should be clearly represented with regard to the main unit and the other clock units for the particular dial. although dial-units are not fundamentally limited to the designation of clock units that are strictly coherent with regard to a decimal expression of the main unit, IDC dial units should feature clock units that are coherent with regard to a decimal expression of the main unit.


specification of decimal dial units

decimal expressions in the IDC system may be designated in terms of a decimal dial, which may be practicably represented in terms of decitriads or decipairs. decitriads consist of an order specifier character or character group that is systematically related to an ordinal group of three decimal places of the main unit, for example, t000 tt000 ttt000. the first decitriad t000 designates the first group of three decimal places of the main unit (0.XXX), the second decitriad tt000 designates the second group of three decimal places (0.xxxXXX), the third decitriad ttt000 designates the third group of three decimal places (0.xxxxxxXXX), and so on. decipairs are designated similarly; however a standard ICAS decipair indicator has not yet been designated (though particular dial or clock unit terms should be used correctly). the practicable use of decitriad or decipair expressions is preferred and encouraged for emerging uses of IDC. however decimal point expression (e.g., 0.5 main IDC) may also be used where practicable.


table 1300.3 ✧ methods of decimal expression

method expression decimal places
first decitriad IDC t000 tenth, hundredth, and thousandth
second decitriad IDC tt000 ten-thousandth, hundred-thousandth, and megaeth
decimal point expression IDC 0.5 main place is designated via decimal point
abridged decitriad 0tt00 or 0tt00 thousandth, ten-thousandth, hundred-thousandth

IDC subminor clock units should be representable in terms of the second decitriad, with a phase duration incrementing the third decimal place of the main unit (0.xxX). however other dial-unit configurations may be designated if practicable. please see AAT ICAS 2220-IDC methods of dial unit decimalization for additional information.

decitriad expressions may also be expressed in terms of an abridged format: for example, '1tt389' is equivalent to 't001 tt389'.


specification of traditional SMH dial

time that is expressed in seconds, minutes, and hours may also be described relative a dial model; however SMH time as such is not expressed as a decimal relative the main unit. for example, SMH time is configured to a 24-hour dial (or 2 repetitions of a 12-hour dial), with 60 minutes per hour and 60 seconds per minute. SMH time is thus not a coherent nor a semi-coherent decimal expression of the main unit.

although SMH scales may be represented in terms of IDC specifications, the use of a SMH system identifier must be used for any implementation of the traditional scale. IDC system identifiers are reserved for dials that implement coherent or semi-coherent decimal expressions of the IDC main unit.


specification of localized times

localized time in IDC is specified as a function of Universal Time (UT) in the form of an offset from UT. particular functions for expressing localized time can take the form zone(z), where z indicates a decitriad value in relation to UT, and where zone indicates a reference to a particular time zone system. the local time midnight UT that may be expressed as IDC z(0)t000 (or as IDC UT t000) thus occurs at the same time as IDC UT (+t250) t250.

the function zoneDeka references a global system that consists typically of 20 zones. particular deka(z) localized times may be expressed within -t450 and +t500 difference from UT, or as applicable.

the function zoneZodiac references a global system that is derived from a model of 24 SMH standard international time zones, each typically representing one hour difference of solar time, using the standard midnight in a zone as a basis for determining IDC zoneZodiac time. particular zodiac(z) localized times are expressed with regard to zodiac(0) equivalent to Universal Time (UT). special implementations of SMH time zones such as daylight savings time or winter time are also expressed relative UT.

with reference to good or best practices for data-interchange, users can also specify the use of a particular localized time zone with reference to the time zone for another location.

top document updated:

system identifiersdatetime
Uniform CalendarUCUCN 12011 X22 White
Inter-Dial ClockIDCzone(UT)t399 tt814
'ICAS in use' can accommodate calendar and clock formatting 'for all people, for all time'.
day of yearD-o-YAD common year day292
Gregorian calendarGG2011 October 19 Wednesday
seconds, minutes, hoursSMHUT09:35:44
style legend


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