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jbranchaud
63 lines
2.2 KiB
Markdown
63 lines
2.2 KiB
Markdown
# Parse Relative Time To datetime Object
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I was looking for an out-of-the-box solution for parsing natural language,
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relative time strings (e.g. `'33 minutes ago'`) into valid `datetime` objects.
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The best library for this is
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[`dateparser`](https://dateparser.readthedocs.io/en/latest/).
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While it is as easy to use this as _import_ then _parse_:
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```python
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>>> import dateparser
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>>> dateparser.parse('33 minutes ago')
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datetime.datetime(2026, 3, 7, 23, 19, 9, 17855)
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```
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There is more to it if we need to deal with timezones.
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In my use case, I wanted to my `datetime` object to be timezone-aware and I
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wanted to store it in `UTC`.
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As is, the above simple `datetime` object is not `tzaware`, meaning it doesn't
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have any `tzinfo` attached to it.
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```python
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>>> dateparser.parse('33 minutes ago').tzinfo is not None
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False
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```
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We need to pass some additional settings during `parse`.
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```python
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>>> settings = {'RETURN_AS_TIMEZONE_AWARE': True}
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>>> dateparser.parse('33 minutes ago', settings=settings)
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>>> _
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datetime.datetime(2026, 3, 8, 9, 53, 36, 225099, tzinfo=zoneinfo.ZoneInfo(key='America/Chicago'))
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>>> settings['TO_TIMEZONE'] = 'UTC'
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>>> dateparser.parse('33 minutes ago', settings=settings)
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>>> _
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datetime.datetime(2026, 3, 8, 14, 54, 47, 34041, tzinfo=<StaticTzInfo 'UTC'>)
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```
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The first step to getting a `datetime` object that is `tzaware` is to set
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`RETURN_AS_TIMEZONE_AWARE` to `True`. That picks up the locale setting of the
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system it is running on -- in my case, I'm in Chicago.
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I said I wanted to store this as UTC though. That means I need to pass an
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additional setting `TO_TIMEZONE` with a value of `'UTC'` which will translate
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the `datetime` from my local time to UTC -- notice the 5 hour difference from
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`9` to `14`.
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Storing `datetime` details like this with timezone info _as_ UTC is nice because
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it keeps everything consistent at the storage layer and then at the presentation
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layer I can always convert it right back to the local timezone with
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`astimezone`.
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```python
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>>> _.astimezone()
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datetime.datetime(2026, 3, 8, 9, 54, 47, 34041, tzinfo=datetime.timezone(datetime.timedelta(days=-1, seconds=68400), 'CDT'))
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```
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See the [`datetime` docs](https://docs.python.org/3/library/datetime.html) for
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more details.
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