known as Greenwich Mean Time, or GMT). This represents a two-hour difference from
the author’s time zone (CET):
In [ 31 ]: dt.datetime.now()
Out[31]: datetime.datetime(2014, 9, 14, 19, 22, 28, 123943)
In [ 32 ]: dt.datetime.utcnow()
# Coordinated Universal Time
Out[32]: datetime.datetime(2014, 9, 14, 17, 22, 28, 240319)
In [ 33 ]: dt.datetime.now() - dt.datetime.utcnow()
# UTC + 2h = CET (summer)
Out[33]: datetime.timedelta(0, 7199, 999982)
Another class of the datetime module is the tzinfo class, a generic time zone class with
methods utcoffset, dst, and tzname. dst stands for Daylight Saving Time (DST). A
definition for UTC time might look as follows:
In [ 34 ]: class UTC(dt.tzinfo):
def utcoffset(self, d):
return dt.timedelta(hours= 0 )
def dst(self, d):
return dt.timedelta(hours= 0 )
def tzname(self, d):
return “UTC”
This can be used as an attribute to a datetime object and be defined via the replace
method:
In [ 35 ]: u = dt.datetime.utcnow()
u = u.replace(tzinfo=UTC())
# attach time zone information
u
Out[35]: datetime.datetime(2014, 9, 14, 17, 22, 28, 597383, tzinfo=<__main__.UTC
object at 0x7f59e496ec10>)
Similarly, the following definition is for CET during the summer:
In [ 36 ]: class CET(dt.tzinfo):
def utcoffset(self, d):
return dt.timedelta(hours= 2 )
def dst(self, d):
return dt.timedelta(hours= 1 )
def tzname(self, d):
return “CET + 1”
Making use of the astimezone method then makes it straightforward to transform the
UTC-based datetime object u into a CET-based one:
In [ 37 ]: u.astimezone(CET())
Out[37]: datetime.datetime(2014, 9, 14, 19, 22, 28, 597383, tzinfo=<__main__.CET
object at 0x7f59e79d8f10>)
There is a Python module available called pytz that implements the most important time
zones from around the world:
In [ 38 ]: import pytz
country_names and country_timezones are dictionaries containing the countries and time
zones covered:
In [ 39 ]: pytz.country_names[‘US’]
Out[39]: u’United States’
In [ 40 ]: pytz.country_timezones[‘BE’]
Out[40]: [u’Europe/Brussels’]
In [ 41 ]: pytz.common_timezones[- 10 :]
Out[41]: [‘Pacific/Wake’,
‘Pacific/Wallis’,
