osd-contiki/apps/time
Ralf Schlatterbeck 0068611b4d Implement localtime
Now we manage a timezone and daylight-savings aware version of
localtime. We parse UNIX timezone strings. The default (active after the
first call to localtime or localtime_r) is CET/CEST, the timezone of
Europe/Vienna. The wallclock-time osd-example demonstrates how to set a
different timezone via the timezone resource.

Note: After startup no timezone is set. So in this state querying the
timezone resource will return an empty string. After first call to
localtime (if not timezone has been set via the timezone resource) a
query to timezone will return the default timezone string for CET/CEST.

The string returned by the localtime and utc timezones now also includes
the timezone name.

New fields tm_gmtoff and tm_zone were added to the tm structure. These
are available in BSD systems and when setting special compiler
definitions on Linux.

Note: the timezone offset information in the tm structure (tm_gmtoff)
as well as in the tz structure returned by gettimeofday (tz_minuteswest)
may be wrong sign, this code is largely untested.
2016-02-18 09:55:07 +01:00
..
Makefile.time Implement localtime 2016-02-18 09:55:07 +01:00
README Implement localtime 2016-02-18 09:55:07 +01:00
resource_gmtime.c Implement localtime 2016-02-18 09:55:07 +01:00
resource_timestamp.c Factor/Fix generic resources 2015-01-21 15:41:21 +01:00
resource_timezone.c Implement localtime 2016-02-18 09:55:07 +01:00
time.c Implement localtime 2016-02-18 09:55:07 +01:00
time.h Implement localtime 2016-02-18 09:55:07 +01:00
time_resource.h Implement localtime 2016-02-18 09:55:07 +01:00
tzparse.h Implement localtime 2016-02-18 09:55:07 +01:00

Timezones
=========

The new version supports time zones and daylight saving time (DST).
Currently we support only a single timezone. We use the UNIX timezone
format which is usually specified in an environment variable TZ.

Note that for timezone information you can have different
representation, either relative to Universal Time Coordinated (UTC) or
to International Atomic Time (TAI), the latter contains leap seconds.
Since most systems today use UTC *and* the clock of a microcontroller
is typically not accurate enough to care about leap seconds, we're using
timezone files relative to UTC.

Wikipedia has a very good treatment of the public timezone database in
https://en.wikipedia.org/wiki/Tz_database

The format of timezone strings is described in the Linux manual page
tzset(3). The timezone specification for Europe/Vienna is
CET-1CEST,M3.5.0,M10.5.0/3