when do I put my period on my tracking calendar?

Elizabeth
I was suppsosed to start on the 21st I had very light spotting just when I wipe it was like that until last night On the 25 when it became heavy while I slept  so do I put that I started last night with just spotting on 21-25 or do I start on 21 with spotting and then heavy on the 26 to continue till I stop I'm not sure