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AAT ICAS 2023 ✧ IDC usage guidelines

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.

this document describes normative AAT ICAS usage guidelines for the Inter-Dial Clock (IDC) system. please refer to AAT ICAS 2020 for additional important usage guidelines, and other AAT ICAS standards for Uniform Calendar specifications and element sets.


Inter-Dial Clock usage guidelines

Inter-Dial Clock terms and expressions should be used to represent uses of IDC scales, methods, and applications. short form terms should only be used if the long form terms are already established.


table 2023.1 ✧ long and short forms of Inter-Dial Clock terms

short form long form
IDC Inter-Dial Clock
Xn main unit chron
t [indicator of decimalization or of decitriad expression]


normative and non-normative usage of terms

this section is directed to outlining guidelines for the normative reference of normative scales of time (for example, references to SI fixed-second or to the ICAS main unit). terms may also be subject to non-normative usage (a figurative reference to no definite quantity or scale of time, for example, 'wait a minute'). this section is not intended to describe guidelines for the non-normative usage of terms. ICAS users and other parties should ensure that the usage of particular terms reflects any scale sensitivity.

there exist a number of various time scales decimalized to a main unit of 1 day. ICAS users and other parties should be alert to certain compatibility issues relating to term usage. in ICAS the normative usage of practical clock terms 'second', 'minute', and 'hour' must be reserved for references to traditional scales of clock or navigation (60 seconds to the minute, 60 minutes to the hour, and so on.). or particularly for the normative usage of 'metric' references, the term 'second' must be reserved for references of the SI fixed-second. ICAS users should use ICAS terms for normative references to IDC scales of decimal time.

other developers have referred to 'metric-seconds', 'metric-minutes', and 'metric-hours' in efforts to explain decimal scales of time; however AAT ICAS strongly advises a reconsideration of these usages. 24-60-60 is not decimal. the SI-second corresponds to 24-60-60. decimal (metric prefix) expressions of the SI-second are formulated exclusive of minutes and hours. to ensure scalar coherence regarding both ICAS and SI: the normative reference to any decimal day scale should use some other term scheme that is exclusive of the terms by which the units in the SMH dials are known.

terms 'second', 'minute', and 'hour' do not clearly represent a decimal subdivision of the practicable clock-unit places in a decimal dial (especially in comparison with a Percent dial), and are moreover not necessary for the communication of common durations of time. a practical solution can be applied: determine the appropriate reference of terms 'tik', 'tok', 'millichron' (or a generic 'millimain'), or 'hubble'.

even apart from reference to particular terms corresponding to a decimal day scale, AAT ICAS strongly encourages other developers to reserve the usage of terms for 'second', 'minute', and 'hour' for references to the traditional 24-60-60 dials. exercising the appropriate and correct use of normative terms is important for developing conformance to a framework of scalar coherence that has been outlined in SI and in ICAS.


usage of main-unit terms and prefixes

the IDC expression 'main unit' is a generic expression for fixed unit measure of time corresponding to the chron. the expression 'fixed day' is also a semi-normative expression for the main unit. for proper usage other than for discussion of IDC concepts however; normative expressions should reflect proper usage appropriate for fixed or coordinated implementations of IDC units.

the main unit 'chron' is lowercased in general use (except for name of element set). IDC prefixes are derived from the following schemes each possessing certain usage conventions: metric prefixes specified by SI, the derived clock unit prefixes (tik and tok), and the coordinating expressions for 'ten' and 'hundred'. SI prefixes are applied to the ICAS main unit as IDC-derived prefixes per SI usage guidelines. for any uses of IDC, the resulting IDC prefixes must only be used with the designated main unit. prefixes must not be used with the traditional equivalent unit of 1 day (for example, millichron NOT milliday, and so on.). prefixes must not be applied from any IDC units other than the designated main unit (for example, millichron, NOT centihubble, and so on.).


table 2023.2 ✧ lexical and symbolic forms of Inter-Dial Clock terms

lexical expressionsymbolic expression
per chron1 Xn-1 = 1 (Xn)-1 = 10-1 Xn
per millichron1 mXn-1 = 1 (mXn)-1 = 10-1 mXn

prefix long or lexical forms are used with the long form of the main unit, and prefix short or symbolic forms are used with the short or symbolic form of the main unit. to enhance or promote consistency of usage; the long and short forms, or the lexical and symbolic forms, should not be mixed in an expression (for example, millichron NOT milliXn, MXn NOT Mchron).

the IDC conventions for usage of metric prefixes also extend to the usage of IDC derived clock unit prefixes. the tikochron (10-5 main or 0.00001 main) and tokochron (10-4 main or 0.0001 main) units comprise two important derived clock units. although these definitions for a decimal prefix-submultiple were devised in extension to the metric prefixes specified by SI, these submultiples of the IDC main unit more closely approximate the SI fixed-second in the terms of a widely referenced measure of a coordinated day that can also be expressed in fixed unit terms. an additional scheme of symbol form is thus designated for units of tikochron and tokochron:


table 2023.3 ✧ IDC derived clock unit prefixes


special note: the expressions 'tiko' and 'toko' (or 'tik' and 'tok') are designated as derived clock unit prefixes of the IDC main unit, subject to provisional specifications described in AAT ICAS 0600.

as the tikochron is exactly 0.864 of the SI fixed-second it is the closest IDC-unit approximation of the fixed-second. a symbol form for the tikochron is used to designate ICAS time-derived measures in the terms of IDC in a manner that is counterpart (similar in dimension yet different in magnitude) to those measures that have been designated in terms of the SI second. please see AAT ICAS 1300 for a table of time-derived units specified for IDC.

for purposes relating to the mathematical expression of scalar values, symbolic forms should be expressed in terms of the IDC main unit or a specified IDC prefix. these forms accommodate the practicable expression of a larger variety of IDC-unit expressions in terms of other particular IDC-unit expressions.

special note: the prior version forms for tikochron (tt01) and tokochron (tt1) were based on decitriad expression. to avoid confusion, exponents should not be applied to decitriad form expressions. consequently the use of the (tt01) and (tt1) symbols is now strongly discouraged. developers and users should note that the ICAS symbol for the ICAS unit of time (chron) is 'Xn', and that the ICAS symbol for tikochron is 'tiXn', and that the ICAS symbol for tokochron is 'toXn'.


usage of main- and clock-unit expressions

a particular implementation of the main unit (or dial-unit of the main unit) may determine the units used to represent times or time quantities. developers and users should consider the appropriate use of:

however coordinated and fixed implementations of the main unit are in many cases highly approximating, and the relative use of particular units may not be limited to a particular fixed or coordinated implementation. regardless of the method of expression, expressions of clock times or units of measure should be formatted or expressed to promote clarity and to ensure consistecy of expression. thus one should format an appropriate number of places for the unit expressed, even if certain places are leading zeros. for example the Tiros unit can be appropriately formatted to 2 numeric places; for example, 'Tiros 01'. additional usage guidelines are described below.


decitriad versus clock-unit expression

developers and users should consider methods of decitriad or decipair expression as appropriate for the normative or formal expression of metric clock times. methods of representing particular major, minor, or subminor clock units for a designated dial unit may be regarded as appropriate for the casual or informal expression of metric clock times. formal expression applies to the use of time quantities as data, while informal expression may be appropriate for the lexical or stylistic representation of clock times. please see AAT ICAS 2200 for additional important information about the design of clock instruments.


usage of decitriad expressions

usage for decimal expressions of the main unit should be represented in the form of decitriads or otherwise by decimal place. the decitriad indicators 't', 'tt', and 'ttt' should always be specified in lowercase by convention, even when expressed in a title or at the beginning of a sentence. decitriad indicators 't', 'tt', 'ttt' should always be used to three decimal places. yet a terminal decitriad indicator may also contain any remainder decimal places.

places beyond the third decitriad may also be expressed more practicably via decimal notation.

abridged decitriad expressions can be useful for the representation of certain minor or subminor clock units. otherwise decitriads should not be abridged. the decimalization indicators may be subscripted, however an abridged decitriad expression must contain only one decimalization indicator, and must only be used unambiguously.


usage of dial units

usage for dial units should be represented in the form of lexical expressions, not in the form of numerical expressions. roman numerals are used as a method of lexical expression that is distinguishable from arabic numerical expressions for certain dial units. numerical forms should only be used in support of the lexical form expressions of dial units. numerical forms should be reserved for time values.

dial unit symbols should be capitalized (initial, part, or all uppercase). main unit symbols and prefixes should be capitalized exactly as specified in the main unit term set. terms 'subminor', 'minor', and 'major' are generic terms, and should not be used as dial or clock unit terms for a particular dial or clock unit (for example, the major unit of the Tiros dial is the Tiros, NOT the Major Unit).


usage of practical clock expressions

practical clock expressions are not capitalized by convention. dial unit identifiers are however capitalized. for example:

ICAS decimalization specifiers 't', 'm', and 'd' should be expressed lowercase wherever lowercasing is available.

a method of clock-code positioning relative a designated bearing (for example, "12 o'clock" designating 'straight ahead' in reference to SMH 12-hour clock dial) may also reference the Tiros dial of 100 major clock units: 'bearing 0 Tiros' for 'straight ahead'; or 'bearing 25 Tiros' for '90 degrees right' of bearing.


preferred formats for the expression of clock times

development note: this section is subject to subsequent designation. the use of particular dials or dial interfaces for particular purposes is under consideration.

developers and users should consider the use of interfaces representing clock dials or clock formats that are coherent to a main unit of 1 day. developers and users should consider the use of decitriad expression for the normative expression of clock times.

developers and users should consider the use of analog clock interfacing in conformance with AAT ICAS 2120 radialDAI specifications. the radialHubble (AAT ICAS 2140) and radialPercent (AAT ICAS 2130) interface specifications provide a strict implementation of radialDAI. please see AAT ICAS 2110 for an overview of specifications for analog interfacing of the decimal dial.


usage of angular coordinates

this section pertains to the use of angular measures for purposes of representing geographical map coordinates, and is subject to further specification for purposes of harmonization with other standards.

AAT ICAS follows the practice for the use of 'degrees' (a circle of 360 angular units) with reference to the 'zodiac' system of some 24 international time zones. for those uses of which degrees are already accommodated and other angular measures are not, users should consider the appropriate use of 'degrees' for map coordinates.

yet for uses of IDC dial 'deka' or 'euclid' time zone systems, users should consider the appropriate use of 'grads' (a circle of 400 angular units). a navigational scale of 400 grads coordinates quite conveniently to a system of 20 time zones. for strict implementations of IDC and ICAS, the usage of degrees is discouraged for reference to 'deka' or 'euclid' time zone systems.

as GPS systems reference locations in terms of meters, AAT ICAS will also review methods for coordinating GPS data to navigational scales, or cite other standards for use with ICAS.

as usage of the term 'grad' has been subject to normative variation, and as the unit is important to ICAS, the designation of ICAS standards for the name and usage of the angular measure is subject to further specification. (short forms of angular measure may include 'DEG', 'GRAD', and 'RAD').

top document updated:

system identifiersdatetime
Uniform CalendarUCUCN 12011 P09 Violet
Inter-Dial ClockIDCzone(UT)t408 tt900
'ICAS in use' can accommodate calendar and clock formatting 'for all people, for all time'.
day of yearD-o-YAD common year day039
Gregorian calendarGG2011 February 08 Tuesday
seconds, minutes, hoursSMHUT09:48:49
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