ekpilot
31 day month.....overtime paid on anything that's creditable over 88 hours.
30 day month.....overtime paid on anything that's creditable over 85 hours.
Credit for the month applies to duties commencing in that month. So, in your example of the JFK, regardless of the flight being conducted into the next day, it's the month in which the duty commences that counts...all of it. That's why you sometimes see a minus sign after the duty if it lands the following day.
Harry