I usually write the flower date on a piece of duct tape, and stick it on the pot.
atleast you have a reference date you can compare to what the plants doing for that week.
I'll look at the date when she went in and date she finished.
if I run that strain again I have a Good ball park idea when it should finish.
alot of the flowering times they give you for a strain are off.
But in the end it all depends on how you want to roll. I keep a loose record in my head.