End of Daylight Savings (clock moved back 1 hr)
Typically 2 AM, last Sunday in October in USA.  The clock moves back from 1:59:59 AM to 1:00:00 AM.

a) Task runs every 1 hour on the hour (i.e. 4:00, 5:00 etc..) or every 30 minutes or every 15 minutes etc..
In this case, the task will run twice at 1 AM on the morning of the time change.  All other schedules will run correctly

b) Task runs daily at 1:00 AM or 1:30 AM or 2:00 AM or 2:30 AM - Task will run correctly on schedule in all cases.

Start of Daylight Savings (clock moved forward 1 hr)
Typically 2 AM, last Sunday in April in USA.  The clock moves forward from 1:59:59 AM to 3:00:00 AM.

a) Task runs every 1 hour on the hour (i.e. 1:00, ..4:00, 5:00 etc..) or every 30 minutes or every 15 minutes etc..
In this case, all scheduled runs between 2:00:00 and 2:59:59 will not run, because this time does not exist.
-  for a task running every hour, you will get 1:00:00 and 3:00:00
- for a task running ever 30 minutes, 1:30:00, 3:00:00, 3:30:00

b) Task runs daily at 1:00 AM or 3:00 AM (i.e. outside the time change window of 1:59:59 - 2:59:59)
The schedule will be correctly at 1:00 AM or 3:00 AM etc.

c) Task runs every day within the time change window (i.e. 2:00 AM - 2:59:59 AM)
In this case, the task will run one hour earlier for 2 days, because this window does not exist, then revert back to the correct schedule

Example: for Apr 6, 2003, time change from 2-3 AM,
A task scheduled every day at 2:00 would run as follows:
Apr 6, 1:00 AM &  Apr 7, 1:00 AM & Apr 7, 2:00 AM, i.e. you will get an extra run
Similarly for a task scheduled daily at 2:30, the runs would be:
Apr 6, 1:30 AM &  Apr 7, 1:30 AM & Apr 7, 2:30 AM