Table of contents
Appendices
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D.1 ISO 8601 Conventions
ISO 8601 Conventions
The primitive datatypes
[duration], [dateTime], [time],
[date], [gYearMonth], [gMonthDay],
[gDay], [gMonth] and [gYear]
use lexical formats inspired by
[ISO8601]. This appendix provides more detail on the ISO
formats and discusses some deviations from them for the datatypes
defined in this specification.
[ISO8601] "specifies the representation of dates in the
proleptic Gregorian calendar and times and representations of periods of time".
The proleptic Gregorian calendar includes dates prior to 1582 (the year it came
into use as an ecclesiastical calendar).
It should be pointed out that the datatypes described in this
specification do not cover all the types of data covered by
[ISO8601], nor do they support all the lexical
representations for those types of data.
[ISO8601] lexical formats are described using "pictures"
in which characters are used in place of digits. For the primitive datatypes
[dateTime], [time],
[date], [gYearMonth], [gMonthDay],
[gDay], [gMonth] and [gYear].
these characters have the following meanings:
-
C -- represents a digit used in the thousands and hundreds components,
the "century" component, of the time element "year". Legal values are
from 0 to 9.
-
Y -- represents a digit used in the tens and units components of the time
element "year". Legal values are from 0 to 9.
-
M -- represents a digit used in the time element "month". The two
digits in a MM format can have values from 1 to 12.
-
D -- represents a digit used in the time element "day". The two digits
in a DD format can have values from 1 to 28 if the month value equals 2,
1 to 29 if the month value equals 2 and the year is a leap year, 1 to 30
if the month value equals 4, 6, 9 or 11, and 1 to 31 if the month value
equals 1, 3, 5, 7, 8, 10 or 12.
-
h -- represents a digit used in the time element "hour". The two digits
in a hh format can have values from 0 to 23.
-
m -- represents a digit used in the time element "minute". The two digits
in a mm format can have values from 0 to 59.
-
s -- represents a digit used in the time element "second". The two
digits in a ss format can have values from 0 to 60. In the formats
described in this specification the whole number of seconds may
be followed by decimal seconds to an arbitrary level of precision.
This is represented in the picture by "ss.sss". A value of 60 or more is
allowed only in the case of leap seconds.
Strictly speaking, a value of
60 or more is not sensible unless the month and day could
represent March 31, June 30, September 30, or December 31 in UTC.
Because the leap second is added or subtracted as the last second of the day
in UTC time, the long (or short) minute could occur at other times in local
time. In cases where the leap second is used with an inappropriate month
and day it, and any fractional seconds, should considered as added or
subtracted from the following minute.
For all the information items indicated by the above characters, leading
zeros are required where indicated.
In addition to the above, certain characters are used as designators
and appear as themselves in lexical formats.
In the lexical format for [duration] the following
characters are also used as designators and appear as themselves in
lexical formats:
-
P -- is used as the time duration designator, preceding a data element
representing a given duration of time.
-
Y -- follows the number of years in a time duration.
-
M -- follows the number of months or minutes in a time duration.
-
D -- follows the number of days in a time duration.
-
H -- follows the number of hours in a time duration.
-
S -- follows the number of seconds in a time duration.
The values of the
Year, Month, Day, Hour and Minutes components are not restricted but
allow an arbitrary integer. Similarly, the value of the Seconds component
allows an arbitrary decimal. Thus, the lexical format for
[duration] and datatypes derived from it
does not follow the alternative
format of § 5.5.3.2.1 of [ISO8601].
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