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julienb74/datetime.py

Forked from temoto/datetime.py
Created March 24, 2012 00:22
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  1. @temoto temoto created this gist Mar 9, 2011.
    62 changes: 62 additions & 0 deletions util/datetime.py
    View file
    Original file line number Diff line number Diff line change
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    # coding: utf-8
    from __future__ import absolute_import
    """Datetime utils.
    To store time use `naive_to_utc(dt, tz_name)`.
    To display time use `utc_to_local(dt, tz_name)`.
    """
    import datetime as stdlib_datetime
    import pytz


    # Emulate stdlib datetime API.
    datetime = pytz.datetime.datetime
    timedelta = stdlib_datetime.timedelta


    def local_to_utc(dt):
    """Converts TZ-aware (with tzinfo) datetime object to UTC time.
    """
    if dt.tzinfo is None:
    raise ValueError(u"dt argument MUST be TZ-aware datetime (with tzinfo). To convert naive datetime, use naive_to_utc.")
    return pytz.utc.normalize(dt.astimezone(pytz.utc))

    def naive_to_local(dt, tz_name):
    """Shortcut for tz = pytz.timezone(tz_name); tz.normalize(tz.localize(dt)).
    """
    tz = pytz.timezone(tz_name)
    return tz.normalize(tz.localize(dt))

    def naive_to_utc(dt, tz_name):
    """Converts naive (w/o tzinfo) datetime object to UTC time.
    `tz_name` must be a symbolic name of time zone of `dt`, e.g. 'Europe/Moscow'.
    Use `os.environ['TZ']` if unsure.
    Shortcut for `naive_to_local(dt, tz_name).astimezone(pytz.utc)` with `dt.tzinfo` check.
    """
    if dt.tzinfo is not None:
    raise ValueError(u"dt argument MUST be naive datetime (w/o tzinfo). To convert TZ-aware datetime, use local_to_utc.")
    return naive_to_local(dt, tz_name).astimezone(pytz.utc)

    def utc_to_local(dt, tz_name):
    """Converts TZ-aware UTC datetime to local for given time zone.
    `tz_name` must be a symbolic name of time zone of `dt`, e.g. 'Europe/Moscow'.
    Use `os.environ['TZ']` if unsure.
    """
    if dt.tzinfo is not pytz.utc:
    raise ValueError(u"dt argument MUST be TZ-aware UTC datetime (with tzinfo = pytz.utc). To convert naive UTC datetime, use dt.replace(tzinfo=pytz.utc).")
    assert dt.tzinfo is pytz.utc
    tz = pytz.timezone(tz_name)
    return dt.astimezone(tz)

    def now_as_local(tz_name):
    """Shortcut for `naive_to_local(datetime.datetime.now, tz_name)`.
    """
    return naive_to_local(datetime.now(), tz_name)

    def now_as_utc(tz_name):
    """Shortcut for `naive_to_utc(datetime.now(), tz_name)`.
    """
    return naive_to_utc(datetime.now(), tz_name)