Isn't the ScheduleTime class doing redundant work? Why bother keeping a dictionary, dealing with ints and strings when you can directly use strftime/strptime?

Except for the friday/fri thing, which, to be honest, I don't see the point of. I'd rather have uniformity in my code.

alternatively: use uWSGI cron

http://uwsgi-docs.readthedocs.org/en/latest/PythonDecorators...

Did anyone else read this title as: 'Scheduling morning meals with Python and Celery'?

While we're on the topic -- there's also http://mailchimp.com/ if you want to outsource the job of sending subscription e-mail.

Would this create a problem around Daylight Saving Time until the user logs in again to reset their time offset?

This doesn't handle daylight saving time.