ISO 8601:2004

Data elements and interchange formats — Information interchange — Representation of dates and times

ISO 8601:2004 is applicable whenever representation of dates in the Gregorian calendar, times in the 24-hour timekeeping system, time intervals and recurring time intervals or of the formats of these representations are included in information interchange. It includes calendar dates expressed in terms of calendar year, calendar month and calendar day of the month; ordinal dates expressed in terms of calendar year and calendar day of the year; week dates expressed in terms of calendar year, calendar week number and calendar day of the week; local time based upon the 24-hour timekeeping system; Coordinated Universal Time of day; local time and the difference from Coordinated Universal Time; combination of date and time of day; time intervals; recurring time intervals. ISO 8601:2004 does not cover dates and times where words are used in the representation and dates and times where characters are not used in the representation. ISO 8601:2004 does not assign any particular meaning or interpretation to any data element that uses representations in accordance with ISO 8601:2004. Such meaning will be determined by the context of the application.

Éléments de données et formats d'échange — Échange d'information — Représentation de la date et de l'heure

General Information

• Status: Withdrawn
• Publication Date: 02-Dec-2004
• Withdrawal Date: 02-Dec-2004
• ICS: 01.140.30 - Documents in administration, commerce and industry
• Technical Committee: ISO/TC 154 - Processes, data elements and documents in commerce, industry and administration
• Drafting Committee: ISO/TC 154 - Processes, data elements and documents in commerce, industry and administration
• Current Stage: 9599 - Withdrawal of International Standard
• Completion Date: 25-Feb-2019
• Directive: TP162 - Zakon o ratifikaciji konvencije o začasnem uvozu

Relations

• Revised: ISO 8601-2:2019 - Date and time — Representations for information interchange — Part 2: Extensions
• Effective Date: 05-Mar-2016
• Revised: ISO 8601-1:2019 - Date and time — Representations for information interchange — Part 1: Basic rules
• Effective Date: 05-Mar-2016
• Revises: ISO 8601:2000 - Data elements and interchange formats — Information interchange — Representation of dates and times
• Effective Date: 15-Apr-2008

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 8601
Third edition
2004-12-01

Data elements and interchange
formats — Information interchange —
Representation of dates and times
Éléments de données et formats d'échange — Échange
d'information — Représentation de la date et de l'heure




Reference number
ISO 8601:2004(E)
©
ISO 2004

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ISO 8601:2004(E)
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ISO 8601:2004(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Terms and definitions. 1
2.1 Basic concepts. 1
2.2 Time units, nominal durations and time intervals . 4
2.3 Representations and formats . 7
3 Fundamental principles. 7
3.1 Basic rules . 7
3.2 Time scales. 8
3.3 Representations and format representations . 10
3.4 Characters used in the representations . 10
3.5 Expansion . 12
3.6 Leading zeros . 12
3.7 Mutual agreement . 12
4 Date and time representations. 13
4.1 Date. 13
4.2 Time of day . 15
4.3 Date and time of day. 18
4.4 Time interval . 20
4.5 Recurring time interval. 23
5 Date and time format representations . 25
Annex A (informative) Relationship to ISO 2014, ISO 2015, ISO 2711, ISO 3307 and ISO 4031 . 26
Annex B (informative) Examples of representations . 27
Bibliography . 33

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ISO 8601:2004(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 8601 was prepared by Technical Committee ISO/TC 154, Processes, data elements and documents in
commerce, industry and administration.
This third edition cancels and replaces the second edition (ISO 8601:2000), of which it constitutes a minor
revision.
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ISO 8601:2004(E)
Introduction
Although ISO Recommendations and Standards in this field have been available since 1971, different forms of
numeric representation of dates and times have been in common use in different countries. Where such
representations are interchanged across national boundaries misinterpretation of the significance of the
numerals can occur, resulting in confusion and other consequential errors or losses. The purpose of this
International Standard is to eliminate the risk of misinterpretation and to avoid the confusion and its
consequences.
This International Standard includes specifications for a numeric representation of information regarding date
and time of day. In addition this International Standard includes specifications for representation of the formats
of these numeric representations.
In order to achieve similar formats for the representations of calendar dates, ordinal dates, dates identified by
week number, time intervals, recurring time intervals, combined date and time of day, and differences
between local time and UTC of day, and to avoid ambiguities between these representations, it has been
necessary to use, apart from numeric characters, either single alphabetic characters or other graphic
characters or a combination of alphabetic and other characters in some of the representations.
The above action has had the benefit of enhancing the versatility and general applicability of previous
International Standards in this field, and provides for the unique representation of any date or time expression
or combination of these. Each representation can be easily recognized, which is beneficial when human
interpretation is required.
This International Standard retains the most commonly used expressions for date and time of day and their
representations from the earlier International Standards and provides unique representations for some new
expressions used in practice. Its application in information interchange, especially between data processing
systems and associated equipment will eliminate errors arising from misinterpretation and the costs these
generate. The promotion of this International Standard will not only facilitate interchange across international
boundaries, but will also improve the portability of software, and will ease problems of communication within
an organization, as well as between organizations.
Several of the alphabetic and graphic characters used in the text of this International Standard are common
both to the representations specified and to normal typographical presentation. Note that for units of time in
plain text the symbols given in ISO 31-1 should be used.
To avoid confusion between the representations and the actual text, its punctuation marks and associated
graphic characters, all the representations are contained in brackets [ ]. The brackets are not part of the
representation, and should be omitted when implementing the representations. All matter outside the brackets
is normal text, and not part of the representation. In the associated examples, the brackets and typographical
markings are omitted.
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INTERNATIONAL STANDARD ISO 8601:2004(E)

Data elements and interchange formats — Information
interchange — Representation of dates and times
1 Scope
This International Standard is applicable whenever representation of dates in the Gregorian calendar, times in
the 24-hour timekeeping system, time intervals and recurring time intervals or of the formats of these
representations are included in information interchange. It includes
 calendar dates expressed in terms of calendar year, calendar month and calendar day of the month;
 ordinal dates expressed in terms of calendar year and calendar day of the year;
 week dates expressed in terms of calendar year, calendar week number and calendar day of the week;
 local time based upon the 24-hour timekeeping system;
 Coordinated Universal Time of day;
 local time and the difference from Coordinated Universal Time;
 combination of date and time of day;
 time intervals;
 recurring time intervals.
This International Standard does not cover dates and times where words are used in the representation and
dates and times where characters are not used in the representation.
This International Standard does not assign any particular meaning or interpretation to any data element that
uses representations in accordance with this International Standard. Such meaning will be determined by the
context of the application.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1 Basic concepts
2.1.1
time axis
mathematical representation of the succession in time of instantaneous events along a unique axis
[IEC 60050-111]
2.1.2
instant
point on the time axis
[IEC 60050-111]
NOTE An instantaneous event occurs at a specific instant.
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ISO 8601:2004(E)
2.1.3
time interval
part of the time axis limited by two instants
[IEC 60050-111]
NOTE A time interval comprises all instants between the two limiting instants and, unless otherwise stated, the
limiting instants themselves.
2.1.4
time scale
system of ordered marks which can be attributed to instants on the time axis, one instant being chosen as the
origin
[IEC 60050-111]
NOTE 1 A time scale may amongst others be chosen as:
— continuous, e.g. international atomic time (TAI) (see IEC 60050-713, item 713-05-18);
— continuous with discontinuities, e.g. Coordinated Universal Time (UTC) due to leap seconds, standard time due to
summer time and winter time;
— successive steps, e.g. usual 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.
NOTE 2 For physical and technical applications, a time scale with quantitative marks is preferred, based on a chosen
initial instant together with a unit of measurement.
NOTE 3 Customary time scales use various units of measurement in combination, such as second, minute, hour, or
various time intervals of the calendar such as calendar day, calendar month and calendar year.
NOTE 4 A time scale has a reference point which attributes one of the marks of the time scale to one of the instants,
thus determining the attribution of marks to instants for the time scale.
2.1.5
time point
date
time
mark attributed to an instant by means of a specified time scale
[IEC 60050-111]
NOTE 1 On a time scale consisting of successive steps, two distinct instants may be expressed by the same time point
(see Note 1 of the term “time scale”).
NOTE 2 For many time scales with quantitative marks, the numerical value of the time point of an instant may also be
considered to be equal to the duration between the origin of the time scale and the considered instant.
NOTE 3 In IEC 60050-111 this definition corresponds with the term “date”.
NOTE 4 The term “time” is often used in common language. However, it should only be used if the meaning is clearly
visible from the context, since the term “time” is also used with other meanings.
2.1.6
duration
non-negative quantity attributed to a time interval, the value of which is equal to the difference between the
time points of the final instant and the initial instant of the time interval, when the time points are quantitative
marks
[IEC 60050-111]
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ISO 8601:2004(E)
NOTE 1 In the case of discontinuities in the time scale, such as a leap second or the change from winter time to
summer time and back, the computation of the duration requires the subtraction or addition of the change of duration of
the discontinuity.
NOTE 2 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.
NOTE 3 For the term “duration”, expressions such as “time” or “time interval” are often used. 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
“time interval”.
NOTE 4 The SI unit of duration is the second.
2.1.7
nominal duration
duration expressed amongst others in years, months, weeks or days
NOTE The duration of a calendar year, a calendar month, a calendar week or a calendar day depends on its position
in the calendar. Therefore, the exact duration of a nominal duration can only be evaluated if the duration of the calendar
years, calendar months, calendar weeks or calendar days used are known.
2.1.8
date
time point representing a calendar day on a time scale consisting of an origin and a succession of calendar
days
NOTE In IEC 60050-111 this definition corresponds with the term “calendar date”.
2.1.9
calendar date
date representing a particular calendar day by its calendar year, its calendar month and its ordinal number
within its calendar month
2.1.10
ordinal date
date representing a particular calendar day by its calendar year and its ordinal number within its calendar year
2.1.11
week date
date representing a particular calendar day by the calendar year to which its calendar week belongs, the
ordinal number of its calendar week within that calendar year and its ordinal number within its calendar week
2.1.12
Coordinated Universal Time
UTC
time scale which forms the basis of a coordinated radio dissemination of standard frequencies and time
signals; it corresponds exactly in rate with international atomic time, but differs from it by an integral number of
seconds
[IEC 60050-713]
NOTE 1 UTC is established by the International Bureau of Weights and Measures (BIPM, i.e. Bureau International des
Poids et Mesures) and the International Earth Rotation Service (IERS). UTC provides the basis of standard time, the use
of which is legal in most countries. The 15th Conférence Géneral des Poids et Mesures (CGPM) (1975) judged in its
Resolution 5 that this usage can be strongly recommended.
NOTE 2 UTC is adjusted to UT1 by the insertion or deletion of seconds, known as “leap seconds”.
NOTE 3 Greenwich Mean Time (GMT) is internationally replaced by UTC. UTC is often (incorrectly) referred to as GMT.
UTC is generally used by aviation and maritime navigation that also uses local apparent time and local mean time for
celestial navigation (see ISO 19018).
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ISO 8601:2004(E)
NOTE 4 Additional information can be found as follows:
— the URL for the ITU http://www.itu.int/itudoc/itu-r/rec/tf/index.html
— the URL for the International Bureau of Weights and Measures http://www.bipm.fr
— the URL for the International Earth Rotation Service http://hpiers.obspm.fr.
2.1.13
UTC of day
quantitative expression marking an instant within a calendar day in accordance with UTC
2.1.14
standard time
time scale derived from coordinated universal time, UTC, by a time shift established in a given location by the
competent authority
[IEC 60050-111]
NOTE This time shift may be varied in the course of a year.
2.1.15
standard time of day
quantitative expression marking an instant within a calendar day by the duration elapsed after midnight in the
local standard time
[IEC 60050-111]
NOTE Standard time of day is called “clock time” in IEC 60050-111.
2.1.16
local time
locally applicable time of day such as standard time of day, or a non-UTC based time of day
2.1.17
recurring time interval
series of consecutive time intervals of the same duration or nominal 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 its end.
2.2 Time units, nominal durations and time intervals
2.2.1
second
base unit of measurement of time in the International System of Units (SI) as defined by the International
Committee of Weights and Measures (CIPM, i.e. Comité International des Poids et Mesures)
NOTE 1 See also ISO 31-1.
NOTE 2 It is the base unit for expressing duration.
2.2.2
leap second
intentional time step of one second to adjust UTC to ensure appropriate agreement with UT1, a time scale
based on the rotation of the Earth
[Rec. ITU-R TF.460-5]
NOTE An inserted second is called positive leap second and an omitted second is called negative leap second. A
positive leap second is inserted between [23:59:59Z] and [24:00:00Z] and can be represented as [23:59:60Z]. Negative
leap seconds are achieved by the omission of [23:59:59Z]. Insertion or omission takes place as determined by IERS,
normally on 30 June or 31 December, but if necessary on 31 March or 30 September.
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ISO 8601:2004(E)
2.2.3
minute
unit of time, equal to 60 seconds
[ISO 31-1]
2.2.4
hour
unit of time, equal to 60 minutes
[ISO 31-1]
2.2.5
day
〈unit of time〉 unit of time, equal to 24 hours
[ISO 31-1]
2.2.6
calendar day
time interval starting at midnight and ending at the next midnight, the latter being also the starting instant of
the next calendar day
NOTE 1 A calendar day is often also referred to as day.
NOTE 2 The duration of a calendar day is 24 hours; except if modified by:
— the insertion or deletion of leap seconds, by decision of the International Earth Rotation Service (IERS), or
— the insertion or deletion of other time intervals, as may be prescribed by local authorities to alter the time scale of local
time.
2.2.7
day
〈duration〉 duration of a calendar day
NOTE The term “day” applies also to the duration of any time interval which starts at a certain time of day at a certain
calendar day and ends at the same time of day at the next calendar day.
2.2.8
calendar week
time interval of seven calendar days starting with a Monday
NOTE 1 A calendar week is often also referred to as week.
NOTE 2 See 3.2.2 for the names of the calendar days and their day numbers.
NOTE 3 A calendar week may be identified by its ordinal number within its calendar year.
2.2.9
week
duration of a calendar week
NOTE The term “week” applies also to the duration of any time interval which starts at a certain time of day at a
certain calendar day and ends at the same time of day at the same calendar day of the next calendar week.
2.2.10
calendar week number
ordinal number which identifies a calendar week within its calendar year according to the rule that the first
calendar week of a year is that one which includes the first Thursday of that year and that the last calendar
week of a calendar year is the week immediately preceding the first calendar week of the next calendar year
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ISO 8601:2004(E)
2.2.11
calendar month
time interval resulting from the division of a calendar year in 12 time intervals, each with a specific name and
containing a specific number of calendar days
NOTE 1 A calendar month is often referred to as month.
NOTE 2 See 3.2.1 for the names of the months of the calendar year in the Gregorian calendar, listed in their order of
occurrence, for their number of days, and for the ordinal dates of the days in common and leap years.
2.2.12
month
duration of 28, 29, 30 or 31 calendar days depending on the start and/or the end of the corresponding time
interval within the specific calendar month
NOTE 1 The term “month” applies also to the duration of any time interval which starts at a certain time of day at a
certain calendar day of the calendar month and ends at the same time of day at the same calendar day of the next
calendar month, if it exists. In other cases the ending calendar day has to be agreed on.
NOTE 2 In certain applications a month is considered as a duration of 30 calendar days.
2.2.13
calendar year
cyclic time interval in a calendar which is required for one revolution of the Earth around the Sun and
approximated to an integral number of calendar days
NOTE 1 A calendar year is often also referred to as year.
NOTE 2 Unless otherwise specified the term designates in this International Standard a calendar year in the Gregorian
calendar.
2.2.14
year
duration of 365 or 366 calendar days depending on the start and/or the end of the corresponding time interval
within the specific calendar year
NOTE The term “year” applies also to the duration of any time interval which starts at a certain time of day at a
certain calendar date of the calendar year and ends at the same time of day at the same calendar date of the next
calendar year, if it exists. In other cases the ending calendar date has to be agreed on.
2.2.15
Gregorian calendar
calendar in general use, introduced in 1582 to define a calendar year that more closely approximated the
tropical year than the Julian calendar
NOTE In this International Standard the term Gregorian calendar is used to refer to the time scale described in 3.2.1.
2.2.16
common year
calendar year in the Gregorian calendar that has 365 calendar days
2.2.17
leap year
calendar year in the Gregorian calendar that has 366 calendar days
2.2.18
centennial year
calendar year in the Gregorian calendar whose year number is divisible without remainder by hundred
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ISO 8601:2004(E)
2.3 Representations and formats
2.3.1
date and time representation
expression indicating a time point, time interval or recurring time interval
2.3.2
date and time format representation
expression describing the format of a group of date and time representations
2.3.3
basic format
format of a date and time representation or date and time format representation comprising the minimum
number of time elements necessary for the accuracy required
NOTE The basic format should be avoided in plain text.
2.3.4
extended format
extension of the basic format that includes additional separators
2.3.5
complete representation
representation that includes all the date and time components associated with the expression; limited, if
applicable, for time elements of representations expressing a calendar year to four digits
2.3.6
decimal representation
expansion of a representation by addition of a decimal fraction to the lowest order component of the
expression
2.3.7
representation with reduced accuracy
abbreviation of a representation by omission of lower order components
2.3.8
expanded representation
expansion of a representation to allow identification of dates in calendar years outside the range [0000] till
[9999]
3 Fundamental principles
3.1 Basic rules
This International Standard gives a set of rules for the representation of
 time points,
 time intervals,
 recurring time intervals.
Both accurate and approximate representations can be identified by means of unique and unambiguous
expressions specifying the relevant dates, times of day and durations. The degree of accuracy required and
obtainable can be varied by including or deleting the appropriate time elements (such as seconds).
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ISO 8601:2004(E)
In addition, this International Standard gives rules for the representation of expressions describing the format
of the above representations.
The decreasing order of time elements, left-to-right, is common to these representations.
3.2 Time scales
3.2.1 The Gregorian calendar
This International Standard uses the Gregorian calendar for the identification of calendar days. This calendar
provides a time scale consisting of a, potentially infinite, series of contiguous calendar years. Consecutive
calendar years are identified by sequentially assigned year numbers.
The Gregorian calendar distinguishes common years of 365 consecutive calendar days and leap years of 366
consecutive calendar days. A leap year is a year whose year number is divisible by four an integral number of
times. However, a centennial year is not a leap year unless its year number is divisible by four hundred an
integral number of times.
In the Gregorian calendar each calendar year is divided in 12 sequential calendar months, each consisting of
a specific number of calendar days as indicated in Table 1.
The Gregorian calendar has a reference point that assigns 20 May 1875 to the calendar day that the
“Convention du Mètre” was signed in Paris.
This International Standard allows the identification of calendar years by their year number for years both
before and after the introduction of the Gregorian calendar. For the determination of calendar years, the year
number and the calendar day within the calendar year only the rules mentioned above are used. For the
purposes of this International Standard the calendar based on these rules is referred to as the Gregorian
calendar. The use of this calendar for dates preceding the introduction of the Gregorian calendar (also called
the proleptic Gregorian calendar) should only be by agreement of the partners in information interchange.
The introduction of the Gregorian calendar included the cancellation of the accumulated inaccuracies of the
Julian calendar. However, no dates shall be inserted or deleted when determining dates in the proleptic
Gregorian calendar.
NOTE In the proleptic Gregorian calendar, the calendar year [0000] is a leap year.
EXAMPLE The Gregorian calendar was introduced on 15 October 1582. In the calendar set by this standard the
calendar day preceding that calendar day is referred to as 14 October 1582. In the Julian calendar that calendar day is
referred to as 4 October 1582.
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ISO 8601:2004(E)
Table 1 — Calendar months
Calendar month Calendar month Number of days in Ordinal dates of the days in Ordinal dates of the
number name the month common years days in leap years
01 January 31 001-031 001-031
28
02 February 032-059 032-060
...