What happens should I add an alarm but set the starting date to a past date?
Does is get executed immediately or is it put in the queue and never executed?
alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, startDate, repeatingValue, alarmIntent);
If the date is in past then alarm will trigger immediately. However you may try to use
setInexactRepeating instead of
alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, startDate, setInexactRepeating , alarmIntent);
From the setInexactRepeating() docs:
Schedule a repeating alarm that has inexact trigger time requirements; for example, an alarm that repeats every hour, but not necessarily at the top of every hour.