Python ISO 8601 date time parser and data model/manipulation utilities
Project description
isodatetime
Python ISO8601 (2004) full-specification parser and data model/manipulation utilities. Intended to be used in a similar way to Python's datetime module.
Installation
Install from PyPI:
$ pip install metomi-isodatetime
Or build yourself:
$ git clone https://github.com/metomi/isodatetime.git isodatetime
$ cd isodatetime
$ python setup.py install
Usage
Python API:
>>> import metomi.isodatetime.parsers as parse
>>> import metomi.isodatetime.dumpers as dump
# Dates and times
>>> date_time = parse.TimePointParser().parse('2000-01-01T00:00Z')
>>> date_time.month_of_year
1
# Durations
>>> duration = parse.DurationParser().parse('P1YT3H')
>>> duration.get_days_and_seconds()
(365.0, 10800.0)
>>> date_time + duration
<metomi.isodatetime.data.TimePoint: 2001-01-01T03:00:00Z>
# Recurrences
>>> recurrence = parse.TimeRecurrenceParser().parse('R/1999/P1Y')
>>> recurrence.get_next(date_time)
<metomi.isodatetime.data.TimePoint: 2001-01-01T00:00:00Z>
# Output
>>> dump.TimePointDumper().strftime(date_time, '%d/%M/%Y %H:%M:%S')
'01/00/2000 00:00:00'
CLI:
$ isodatetime
2000-01-01T00:00:00Z
$ isodatetime 1066
1066
$ isodatetime 1066 --offset P1Y
1067
$ isodatetime R/2000/P1Y --max 3
2000-01-01T00:00:00Z
2001-01-01T00:00:00Z
2002-01-01T00:00:00Z
Copyright and Terms of Use
Copyright (C) 2013-2023 British Crown (Met Office) & Contributors.
This program is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU Lesser General Public License along with this program. If not, see GNU licenses.
ISO 8601
ISO 8601 (2004) is an international standard for writing down date/time information.
It is the correct, internationally-friendly, computer-sortable way to numerically represent date/time information.
Good reading material:
Reference material:
Dates and times
How do I write the year, month-of-year, and day-of-month down?
Syntax | Example |
---|---|
CCYYMMDD | 20151231 |
CCYY-MM-DD | 2015-12-31 |
How about writing down the year, week-of-year, and day-of-week?
Syntax | Example |
---|---|
CCYYWwwD | 2015W534 |
CCYY-Www-D | 2015-W53-4 |
How about writing down the year and day-of-year?
Syntax | Example |
---|---|
CCYYDDD | 2015365 |
CCYY-DDD | 2015-365 |
How do I write just the year?
Either:
CCYY
or
+XCCYY
+X
stands for a plus or minus sign (+
or -
), followed by a fixed,
agreed number of expanded year digits (X
). For example, if we agree to have
2 expanded year digits, we can represent years from -999999 to +999999
(1000000 BC to 999999 AD). Note that 1 BC is the year 0 in the proleptic
Gregorian calendar used by ISO 8601.
For example, you can write the year 1995 AD as:
1995
or
+001995
(using 2 expanded year digits).
Note: writing just the year where you mean a proper date implies Day 1 of
Month 1 in that year - 1995
implies 1995-01
=> 1995-01-01
=>
1995-01-01T00
=> 1995-01-01T00:00
=> 1995-01-01T00:00:00
.
How do I write just the year and month-of-year?
Either:
CCYY-MM
or
+XCCYY-MM
(+ standing in here for a +
or -
sign)
(not allowed: CCYYMM
or +XCCYYMM
).
How do I write dates past the year 9999 and before 0000?
Syntax | Example (2 expanded year digits) |
---|---|
+XCCYYMMDD | +0020151231 |
+XCCYY-MM-DD | +002015-12-31 |
+XCCYYWwwD | +002015W534 |
+XCCYY-Www-D | +002015-W53-4 |
+XCCYYDDD | +002015365 |
+XCCYY-DDD | +002015-365 |
How do I write down time information by itself?
Syntax | Example |
---|---|
hhmmss | 083000 |
hhmm | 0830 |
hh:mm:ss | 17:45:01 |
hh:mm | 17:45 |
hh | 08 |
How do I write down time information at a date in ISO 8601?
Write the time after the date, separated with a T
:
Syntax | Example |
---|---|
CCYYMMDDThhmmss | 20151231T063101 |
CCYY-MM-DDThh:mm:ss | 2015-12-31T06:31:01 |
CCYYWwwDThhmmss | 2015W534T063101 |
CCYY-Www-DThh:mm:ss | 2015-W53-4T06:31:01 |
CCYYDDDThhmmss | 2015365T063101 |
CCYY-DDDThh:mm:ss | 2015-365T06:31:01 |
What about just the hour and minute at a date?
Syntax | Example |
---|---|
CCYYWwwDThhmm | 2015W534T0631 |
CCYY-Www-DThh:mm | 2015-W53-4T06:31 |
What about just the hour at a date?
Syntax | Example |
---|---|
CCYYMMDDThh | 20151231T06 |
CCYY-MM-DDThh | 2015-12-31T06 |
What about decimal parts of the hour or minute or second?
Use a comma or period to delimit the decimal part, and don't include any smaller units:
Syntax | Example |
---|---|
CCYYMMDDThh,ii | 20151231T06,5 |
CCYYMMDDThh.ii | 20151231T06.5 |
CCYYMMDDThhmm,nn | 20151231T0631,3333 |
CCYYMMDDThhmm.nn | 20151231T0631.3333 |
CCYYMMDDThhmmss,tt | 20151231T063101,25671 |
CCYYMMDDThhmmss.tt | 20151231T063101.25671 |
How do I specify a time zone?
If the time zone is UTC, use "Z" - otherwise, use a numeric representation of the hours and minutes difference from UTC.
Note that this difference is (TIMEZONE - UTC) - so longitudes east of 0 tend to have positive differences, and west of 0 usually have negative differences.
Syntax | Example |
---|---|
CCYYMMDDThhmmssZ | 20151231T063101Z |
CCYY-MM-DDThh:mm:ssZ | 2015-12-31T06:31:01Z |
CCYYMMDDThhmmss-hh | 20151231T013101-05 |
CCYY-MM-DDThh:mm:ss-hh | 2015-12-31T01:31:01-05 |
CCYYMMDDThhmmss+hh | 20151231T083101+02 |
CCYY-MM-DDThh:mm:ss+hh | 2015-12-31T08:31:01+02 |
CCYYMMDDThhmmss-hhmm | 20151230T203101-1000 |
CCYY-MM-DDThh:mm:ss-hh:mm | 2015-12-30T20:31:01-10:00 |
CCYYMMDDThhmmss+hhmm | 20151231T193101+1300 |
CCYY-MM-DDThh:mm:ss+hh:mm | 2015-12-31T19:31:01+13:00 |
Durations
How do I write down a certain period of time in X units?
A "P" followed by the number of units (optionally including a decimal part) followed by a designator to mark the units:
Unit type | Unit designator |
---|---|
years | Y |
months | M |
weeks | W |
days | D |
hours | H |
minutes | M |
seconds | S |
If the unit is one of hours, minutes, or seconds, you need a leading "T" to delimit time from date:
Syntax | Example | Meaning |
---|---|---|
PnY | P2Y | 2 years |
PTnM | PT7M | 7 minutes (note the 'T') |
PnM | P10M | 10 months |
PnDTnH | P5DT6H | 5 days and 6 hours |
PTn,oH | PT5,5H | 5 and a half hours |
PTn.oH | PT5.5H | 5 and a half hours |
PnW | P2W | 2 weeks |
Combining any other unit with weeks is not allowed. Decimals may only be used for hours, minutes and seconds.
Note that years and months are "nominal" durations, whose exact length of time depends on their position in the calendar. E.g., a duration of 1 calendar year starts on a particular day of a particular month and ends on the same day of the same month in the following calendar year, and may be different to 365 days in the Gregorian calendar due to leap years.
Conversely, weeks, days, hours, minutes and seconds are exact units, so
P1W == P7D
, P1D == PT24H
and PT1H == PT60M
etc. are always true.
(Although ISO 8601 specifies that weeks and days are nominal durations, there
is no case where they are not exact in our implementation.)
A supplementary format (which has to be agreed in advance) is to specify a
date-time-like duration (PCCYY-MM-DDThh:mm:ss
) where the numbers given for
years, months, days, hours, minutes, and seconds are used literally
(P1995-00-00T00:10:00
= P1995YT10M
).
Recurring date-time series
1. Recur with a duration given by the difference between a start date and a subsequent date
Example Syntax | Example | Meaning |
---|---|---|
R/CCYY/CCYY | R/2010/2014 | Repeat every 1461 days (≈ 4 years*), starting at 2010-01-01 |
R/CCYY-MM/CCYY-DDD | R/2010-01/2012-045 | Repeat every 774 days (≈ 2 years and 44 days*), starting at 2010-01-01 |
Rn/CCYY-Www-D/CCYY-Www-D | R5/2015-W05-2/2015-W07-3 | Repeat every 15 days (= 2 weeks and 1 day), five times, starting at 2015-W05-2 |
Rn/CCYY-MM-DDThh/CCYY-MM-DDThh | R1/1925-02-11T00Z/2027-06-01T00Z | Repeat once at 1925-02-11T00Z (note the end date-time is ignored) |
*See the previous section as to why only an approximate equivalent number of years are given.
2. Recur with a specified duration, starting at a context date-time
(You have to supply the context somewhere else)
Example Syntax | Example | Meaning |
---|---|---|
R/PnMnDTnM | R/P10M3DT45M | Repeat every 10 months, 3 days, and 45 minutes from a context start date-time. |
Rn/PnY | R2/P4Y | Repeat every 4 years, for a total of 2 times, from a context start date-time. |
3. Recur with a specified duration starting at a particular date-time
Example Syntax | Example | Meaning |
---|---|---|
R/CCYYMMDDThhZ/PTnH | R/20201231T00Z/PT12H | Repeat every 12 hours starting at 2020-12-31T00Z |
R/CCYY-Www-D/PnW | R/2012-W02-1/P1W | Repeat weekly starting at Monday in the second ISO week of 2012 |
R/CCYYDDDThhmm/PnD | R/1996291T0630+0100/P2D | Repeat every 2 days starting on the 291st day of 1996 at 06:30, UTC + 1 |
Rn/CCYY-MM-DDThh:mm/PTnH | R2/19900201T06Z/PT12H | Repeat every 12 hours, for a total of 2 repetitions, starting at 1990-02-01T06Z |
Rn/CCYY-Www-D/PnW | R5/2012-W02-1/P1W | Repeat weekly, for a total of 5 repetitions, starting at Monday in the second ISO week of 2012 |
Rn/CCYYDDDThhmm/PnD | R1/1996291T0630Z/P2D | Repeat once on the 291st day of 1996 at 06:30 (note the duration is ignored) |
4. Recur with a specified duration ending at a particular date-time
The starting date-time of the recurrence is calculated from the specified duration.
Example Syntax | Example | Meaning |
---|---|---|
R/PTnH/CCYY-MM-DDThhZ | R/PT1H/2012-01-02T00Z | Repeat hourly, ending at 2012-01-02T00Z (therefore repeats on the hour) |
R/PnY/CCYY | R/P3Y/2000 | Repeat every 3 years, ending at 2000-01-01 (therefore repeats at 00:00 January 1st) |
R/PTnS/+XCCYYDDDThhmm | R/PT5s/-002500012T1800 | Repeat every 5 seconds, ending on the 12th day in 2501 BC at 18:00 (using 2 expanded year digits) |
Rn/PnYTnM/CCYY-MM-DDThhZ | R5/P1YT5M/2012-01-02T00Z | Repeat every year and 5 minutes, five times, ending at 2012-01-02T00Z |
Rn/PnM/CCYY-MM | R4/P1M/2000-05 | Repeat monthly, four times, ending at 2000-05-01 (therefore repeats on the first of the month) |
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