Data Loader applies Daylight Savings Time changes to all tasks except biweekly tasks.
When Daylight Savings Time goes into effect, tasks scheduled to run between 2:00 a.m. and 2:59 a.m. don't run the day the time changes from 2:00 a.m. to 3:00 a.m.. If a task is scheduled to run biweekly at 2:00 a.m., it will run at 3:00 a.m. the day of the time change, and at 2:00 a.m. after that.
Daylight Savings Time doesn't trigger additional runs for tasks that are scheduled to run between 1:00 a.m. and 1:59 a.m. when Standard Time begins. For example, a task is scheduled to run every day at 1:30 a.m.. When the time changes from 2:00 a.m. to 1:00 a.m., the task doesn't run again at 1:30 a.m..
Tip: To make sure that Data Loader doesn't skip any scheduled runs near the 2:00 a.m. time change, don't schedule tasks to run between 12:59 a.m. and 3:01 a.m..