time.tzset()

time.tzset()

Resets the time conversion rules used by the library routines. The environment variable TZ specifies how this is done.

Availability: Unix.

The standard format of the TZ environment variable is (whitespace added for clarity):

std offset [dst [offset [,start[/time], end[/time]]]]

Where the components are:

std and dst

Three or more alphanumerics giving the timezone abbreviations. These will be propagated into time.tzname

offset

The offset has the form: ± hh[:mm[:ss]]. This indicates the value added the local time to arrive at UTC. If preceded by a ‘-‘, the timezone is east of the Prime Meridian; otherwise, it is west. If no offset follows dst, summer time is assumed to be one hour ahead of standard time.

start[/time], end[/time]

Indicates when to change to and back from DST. The format of the start and end dates are one of the following:

Jn

The Julian day n (1 <= n <= 365). Leap days are not counted, so in all years February 28 is day 59 and March 1 is day 60.

n

The zero-based Julian day (0 <= n <= 365). Leap days are counted, and it is possible to refer to February 29.

Mm.n.d

The d‘th day (0 <= d <= 6) or week n of month m of the year (1 <= n <= 5, 1 <= m <= 12, where week 5 means “the last d day in month m” which may occur in either the fourth or the fifth week). Week 1 is the first week in which the d‘th day occurs. Day zero is Sunday.

time has the same format as offset except that no leading sign (‘-‘ or ‘+’) is allowed. The default, if time is not given, is 02:00:00.

>>> os.environ['TZ'] = 'EST+05EDT,M4.1.0,M10.5.0'
>>> time.tzset()
>>> time.strftime('%X %x %Z')
'02:07:36 05/08/03 EDT'
>>> os.environ['TZ'] = 'AEST-10AEDT-11,M10.5.0,M3.5.0'
>>> time.tzset()
>>> time.strftime('%X %x %Z')
'16:08:12 05/08/03 AEST'

On many Unix systems (including *BSD, Linux, Solaris, and Darwin), it is more convenient to use the system’s zoneinfo (tzfile(5)) database to specify the timezone rules. To do this, set the TZ environment variable to the path of the required timezone datafile, relative to the root of the systems ‘zoneinfo’ timezone database, usually located at /usr/share/zoneinfo. For example, 'US/Eastern', 'Australia/Melbourne', 'Egypt' or 'Europe/Amsterdam'.

>>> os.environ['TZ'] = 'US/Eastern'
>>> time.tzset()
>>> time.tzname
('EST', 'EDT')
>>> os.environ['TZ'] = 'Egypt'
>>> time.tzset()
>>> time.tzname
('EET', 'EEST')