Binand Sethumadhavan wrote:
Today (or rather, tonight) is when most of North America switches to
Daylight Saving Time. I am curious how Linux cron deals with this
change. I'd imagine:
Spring and Autumn Time Transitions
On the days of daylight savings (summer) time transition (in time zones and
countries where daylight savings time applies), cron schedules commands
differently from normal.
In the following description, an ambiguous time refers to an hour and minute
that occurs twice in the same day because of a daylight savings time
transition (usually on a day during the Autumn season). A nonexistent time
refers to an hour and minute that does not occur because of a daylight
savings time transition (usually on a day during the Spring season).
DST-shift refers to the offset that is applied to standard time to result in
daylight savings time. This is normally one hour, but can be any combination
of hours and minutes up to 23 hours and 59 minutes (see tztab(4)).
When a command is specified to run at an ambiguous time, the command is
executed only once at the first occurrence of the ambiguous time.
When a command is specified to run at a nonexistent time, the command is
executed after the specified time by an amount of time equal to the
DST-shift. When such an adjustment would conflict with another time specified
to run the command, the command is run only once rather than running the
command twice at the same time.
Commands that are scheduled to run during all hours (there is a * is in the
hour field of the crontab entry) are scheduled without any adjustment.
