BDing in the early morning?

Megan • My DH & I have been together 1 1/2 yrs. I brought 3 kids & he brought 2. Just found out #6 is on it's way!!!!!!!!
My husband and I often BD at 3 or 4 am. I'm wondering when we do this which day does it count as when marking my calander? I don't use opks so this is the only way I keep track. So if tonight we bd at 3 am do I mark it today or tomorrow since it's after midnight?