I just noticed a crontab task setup to run at 12:00 today for some reason ran at at
both 11:00 and then again at 12:00. I've checked the server date and time and it does seem to have made the switch to winter time last night so i'm not sure if this was a fluke or really related to the DST but i don't see any other reason for it to run the task twice...

My crontab setup, for this particular task, looks like this:

from celery.schedules import crontab

CELERYBEAT_SCHEDULE = {
    'event_suggestions': {
        'task': 'events.event_suggestions',
        'schedule': crontab(hour=12, minute=0, day_of_week=1)
    }
}

Versions are:
celery==3.0.24
django-celery==3.0.23