You have to count the days. Keep a calendar. Actually you have to count the nights. If they sleep at your home that counts as a day that they lived with you. If they sleep at Dad's home it counts as a day that they lived with him.
The number of months that you enter in TurboTax is not precise. It's the days (or nights) that matter, not the months. If they lived with you more than half the nights during the year, enter 7 months or more. If they lived with you less than half the nights during the year, enter 5 months or less.
