Qore Programming Language Reference Manual 1.16.0
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Time Zone Handling

Qore assumes a default time zone for all programs when it starts up. The rules for determining the default time zone are similar to those for the C library in most UNIX or UNIX-like operating systems.

UNIX Time Zone Handling

If the TZ environment variable is defined, then the contents of that variable are used to find a zoneinfo file that contains the time zone definition. If this file cannot be found, then the default time zone will default to UTC.

If the TZ environment variable is not defined or is empty, then the Qore library tries to find the default zoneinfo definition file (normally /etc/localtime). If found, this file is read in and provides the information about the local time zone. If not found, the default time zone will default to UTC.

When a zoneinfo file is found, information about local time zone names and daylight savings time is available for times tagged with that time zone.

Note that posix-style time zone rules are not understood if assigned to the TZ environment variable, only file names to a zoneinfo file can be processed at the moment. Furthermore if the zoneinfo file contains leap second information, it is currently ignored.

Windows Time Zone Handling

Time zone information is read in from binary time zone data in the Windows registry under:

  • HKEY_LOCAL_MACHINE SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones

Time zone region names must correspond to registry keys under the above key or to zoneinfo names (which will be temporarily converted to the corresponding Windows registry keys according to a lookup table), otherwise the time zone information will not be loaded.

The region name reported by Qore::TimeZone::region() will be the zoneinfo name passed to TimeZone's constructor or a zoneinfo name corresponding to the Windows-style name (first corresponding zoneinfo name according to alphabet).

For example:

O:\bin>qore -ne "TimeZone tz('Central Europe Standard Time'); printf(\"%s\n\", tz.region());"

O:\bin>qore -ne "TimeZone tz('Europe/Vienna'); printf(\"%s\n\", tz.region());"

More Time Zone Information and Examples

See the Qore::TimeZone class for information about retrieving, setting, and querying time zone information; see Date and Time Functions for a list of functions related to date/time processing.

Here are some examples using Qore's '-X' option for evaluating an expression and displaying the result immediately:

prompt% TZ=America/Chicago qore -X 'now_us()'
2010-05-11 06:14:28.845857 Tue -05:00 (CDT)
prompt% TZ=Europe/Rome qore -X 'now_us()'
2010-05-11 13:14:35.070568 Tue +02:00 (CEST)
prompt% TZ=Australia/Sydney qore -X 'now_us()'
2010-05-11 21:14:45.422222 Tue +10:00 (EST)
prompt% TZ=Asia/Tokyo qore -X 'now_us()'
2010-05-11 20:14:59.609249 Tue +09:00 (CJT)