GB/T 7408.1-2023 Date and time - Representations for information interchange - Part 1: Basic rules
1 Scope
This document specifies representations of dates of the Gregorian calendar and times based on the 24?hour clock.
This document applies to the representation of dates and times in information exchange. It is also applicable for representing times and time shifts based on Coordinated Universal Time (UTC).
This document excludes the representation of date elements from non?Gregorian calendars or times not from the 24?hour clock. This document does not address character encoding of representations specified in this document.
2 Normative references
There are no normative references in this document.
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1.1 Basic concepts
3.1.1.1
date
time on the calendar time scale
Note: Common forms of date include calendar date, ordinal date or week date.
3.1.1.2
time
mark attributed to an instant or a time interval on a specified time scale
Note 1: The term “time” is often used in common language. However, it should only be used if the meaning is clearly visible from the context.
Note 2: On a time scale consisting of successive time intervals, such as a clock or calendar, distinct instants may be expressed by the same time.
Note 3: This definition corresponds with the definition of the term “date” in IEC 60050?113:2011, 113?01?12.
3.1.1.3
instant
point on the time axis
Note: An instantaneous event occurs at a specific instant.
[SOURCE: IEC 60050?113:2011, 113?01?08]
3.1.1.4
time axis
mathematical representation of the succession in time according to the space?time model of instantaneous events along a unique axis
Note 1: According to the theory of special relativity, the time axis depends on the choice of a spatial reference frame.
Note 2: In GB/T 2900.93-2015, 113-01-03, time according to the space-time model is defined to be the one?dimensional subspace of space?time, locally orthogonal to space.
[SOURCE: IEC 60050-113:2011, 113-01-07, modified]
3.1.1.5
time scale
system of ordered marks which can be attributed to instants on the time axis, one instant being chosen as the origin
Note: A time scale may amongst others be chosen as:
——continuous, e.g. international atomic time (TAI) (see GB/T 2900.54-2002, 713-05-18);
——continuous with discontinuities, e.g. UTC due to leap seconds, standard time due to summer time and winter time;
——successive steps, e.g. calendars, where the time axis is split up into a succession of consecutive time intervals and the same mark is attributed to all instants of each time interval;
——discrete, e.g. in digital techniques.
[SOURCE: IEC 60050-113:2011, 113-01-11, modified]
3.1.1.6
time interval
part of the time axis limited by two instants and, unless otherwise stated, the limiting instants themselves
[SOURCE: IEC 60050-113:2011, 113-01-10, modified]
3.1.1.7
time scale unit
unit of measurement of a duration
Example 1: Calendar year, calendar month and calendar day are time scale units of the Gregorian calendar.
Example 2: Clock hour, clock minutes and clock seconds are time scale units of the 24?hour clock.
3.1.1.8
duration
non-negative quantity of time equal to the difference between the final and initial instants of a time interval
Note 1: The duration is one of the base quantities in the International System of Quantities (ISQ) on which the International System of Units (SI) is based. The term “time” instead of “duration” is often used in this context and also for an infinitesimal duration.
Note 2: For the term “duration”, expressions such as “time” or “time interval” are often used, but the term “time” is not recommended in this sense and the term “time interval” is deprecated in this sense to avoid confusion with the concept of “time interval”.
Note 3: The exact duration of a time scale unit depends on the time scale used. For example, the durations of a year, month, week, day, hour or minute, may depend on when they occur [in a Gregorian calendar, a calendar month can have a duration of 28, 29, 30, or 31 days; in a 24-hour clock, a clock minute can have a duration of 59, 60, or 61 seconds, etc.]. Therefore, the exact duration can only be evaluated if the exact duration of each is known.
Note 4: This definition is closely related to NOTE 1 of the terminological entry “duration” in IEC 60050?113:2011, 113?01?13.
3.1.1.9
clock
time scale suited for intra?day time measurements
Example 1: The 24-hour clock is a type of clock.
Example 2: clock second, clock minute and clock hour are often time scale units included in a clock.
3.1.1.10
24-hour clock
clock that subdivides a calendar day into 24 clock hours
Note: UTC forms the basis of today’s 24?hour clocks and is used in this document as a type of 24?hour clock, as described in 4.2.3.
3.1.1.11
recurring time interval
series of consecutive time intervals of identical duration
Note: If the duration of the time intervals is measured in calendar entities, the duration of each time interval depends on the calendar dates of its start and end.
3.1.1.12
Coordinated Universal Time
UTC
time scale with the same rate as International Atomic Time (TAI), but differing from TAI only by an integral number of seconds
Note 1: UTC is the time standard commonly used across the world from which local time is derived.
Note 2: UTC is produced by the Bureau International des Poids et Mesures (BIPM), i.e. the International Bureau of Weights and Measures.
Note 3: TAI is a continuous time scale produced by the BIPM based on the best realizations of the SI second. TAI is a realization of Terrestrial Time (TT) with the same rate as that of TT, as defined by the International Astronomical Union Resolution B1.9 (2000).
[SOURCE: BIPM Recommendation CCTF 3 (2017), modified]
3.1.1.13
UTC of day
time of day in UTC
3.1.1.14
standard time
time scale derived from UTC, by a time shift established in a given location by the competent authority
Example 1: Some standard times do not vary within a year, such as US Eastern Standard Time (EST), US Eastern Daylight Time (EDT), Australia Western Standard Time (AWST), China Standard Time (CST), Hong Kong Standard Time (HKT), Korea Standard Time (KST) and Japanese Standard Time (JST).
Example 2: Some standard times vary within a year, such as US Eastern Time (ET) and Australian Central Standard Time (ACST).
Note: The time shift of a standard time may vary in the course of a year, such as due to daylight savings.
[SOURCE: IEC 60050-113:2011, 113-01-17, modified]
3.1.1.15
local time scale
locally?applicable time scale such as standard time or a non?UTC based time scale
3.1.1.16
time of day
time occurring within a calendar day
Note 1: Generally, time of day relates to the duration elapsed after the beginning of the day. However, this correlation breaks when changes occur in the time scale that applies to the time of day, such as time shifts and leap seconds.
Note 2: This definition corresponds closely with the definition of “clock time” given in IEC 60050?113:2011, 113-01-18, except that the concepts of duration and time scale are not used in this definition.
3.1.1.17
local time of day
time of day (3.1.1.16) in a local time scale
3.1.1.18
calendar
time scale that uses the time scale unit of calendar day as its basic unit
Example: The Gregorian calendar is a type of calendar.
Note: calendar month and calendar year are time scale units often included in a calendar.
3.1.1.19
Gregorian calendar
calendar in general use that defines a calendar year that closely approximates the tropical year
Note: In this document the term “Gregorian calendar” is used to refer to the time scale described in 4.2.1.
