Luteal Lunacy

After ovulation you go into the luteal phase where you produce progesterone which in turn increases your temperature. The higher temperature acts like an incubator which is important in maturing a fertilized egg if conception has occurred. Usually you need a minimum of a 10 day luteal phase for successful implantation. Implantaition is sometimes marked with a brief spotting. Since a woman's luteal phase is very consistent each cycle if you reach day 18 of your luteal phase and have not had a period, there is a very good possibility that pregnancy has occurred.

By the way I have 15 more days left from the original 18 - so that's 360 more hours to go.