ISO 8601-1:2019/Amd 1:2022

INTERNATIONAL ISO
STANDARD 8601-1
First edition
2019-02
AMENDMENT 1
2022-10
Date and time — Representations for
information interchange —
Part 1:
Basic rules
AMENDMENT 1: Technical corrections
Date et heure — Représentations pour l'échange d'information —
Partie 1: Règles de base
AMENDEMENT 1: Corrections techniques
Reference number
ISO 8601-1:2019/Amd.1:2022(E)
ISO 8601-1:2019/Amd.1:2022(E)
© ISO 2022
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ii
ISO 8601-1:2019/Amd.1:2022(E)
Foreword
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iii
ISO 8601-1:2019/Amd.1:2022(E)
Date and time — Representations for information
interchange —
Part 1:
Basic rules
AMENDMENT 1: Technical corrections

3.1.1.24
Replace “Note 2 to entry” with the following:
Note 2 to entry: An inserted second is called a positive leap second and an omitted second is called
a negative leap second. A positive leap second is inserted after [23:59:59Z] as the last second of that
minute, which is represented as [23:59:60Z]. A negative leap second is achieved by the omission
of [23:59:59Z], where the last second of that minute is represented as [23:59:58Z]. Insertion or
omission takes place as determined by the International Earth Rotation and Reference Systems
Service (IERS), normally on 30 June or 31 December, but if necessary on 31 March or 30 September.

3.1.2.15
Replace “Note 1 to entry” with the following:
Note 1 to entry: The term “week” applies also to the duration of any time interval (3.1.1.6) which
starts at a certain time of day (3.1.1.16) at a certain calendar day of week (3.1.2.12) and ends at the
same time of day at the same calendar day of week in the next calendar week.

4.2.2
Replace “NOTE” with the following:
NOTE The calendar year used in the week calendar and the Gregorian calendar are
independent units and do not necessarily align. An identical day as referenced in the week calendar
and the Gregorian calendar can belong to different calendar years in their respective calendars. For
instance, the first day of 2019 Week 1 (a Monday) in the week calendar is actually 2018-12-31 in the
Gregorian calendar.
4.2.2
Move the NOTE to before Table 2.

4.2.3, first paragraph
Replace the paragraph with the following:
ISO 8601-1:2019/Amd.1:2022(E)
This document uses the 24-hour clock for identification of times within a calendar day, where the
duration of a calendar day is defined as 24 clock hours, the duration of a clock hour as 60 clock
minutes, and the duration of a clock minute generally as 60 clock seconds (except when insertion of
a positive leap second or omission of a negative leap second occurs).

4.3.2
Add the following paragraph after the first paragraph:
The year number may be preceded by a minus sign to indicate a year preceding year zero.

4.3.2, third paragraph
Replace the paragraph with the following:
The number of digits may exceed 4 in the case of expanded representation.

4.3.11
Add the following paragraph as the first paragraph:
Each Gregorian calendar decade is identified by a 3-digit ordinal number beginning with ‘000’, for
decade zero, through ‘999’.
4.3.12
Add the following paragraph as the first paragraph:
Each Gregorian calendar century is identified by a 2-digit ordinal number beginning with ‘00’, for
century zero, through ‘99’.
5.3.1.4, first paragraph
Replace the paragraph with the following:
A decimal fraction of hour, minute or second may be included in a representation. If included, lower
order time scale components (if any) shall be omitted and the decimal fraction shall be divided
from the integer part by the decimal sign. If the magnitude of the number is less than one, the
decimal sign shall be preceded by two zeros in accordance with 4.5.

5.3.2
Replace the subclause title of “Beginning of day” with “Beginning of the day, ending of the day”.

ISO 8601-1:2019/Amd.1:2022(E)
5.3.2
Replace the text with the following:
The beginning of the day is defined as the first instant of the day, and the ending of the day is
defined as the last instant of the day, where the last instant of the day is identical to the first instant
of the next day.
NOTE 1 An instant does not have any duration.
For disambiguation and semantic needs, despite that the last instant of the day is technically also
the first instant of the next day, separate expressions are used to differentiate these two cases.
As time of day relates to the duration elapsed since the first instant of the day:
— the “beginning of the day” expressions represent that no time has elapsed since the first instant
of the day;
— the “ending of the day” expressions represent that 24 hours have elapsed since the first instant
of the day.
NOTE 2  This document does not explicitly distinguish the representation of instants from time intervals.
Expressions of the beginning of the day and the ending of the day conform with representations of
time of day.
The expressions, as complete representations in basic and extended format for the beginning of the
day and the ending of the day, in accordance with 5.3.1, are as follows:
a) Beginning of the day
Basic format: T000000 (in the format of 5.3.1.2 a))
Extended format: 00:00:00 (or T00: 00: 00) (in the format of 5.3.1.2 b))
b) Ending of the day
Basic fo
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