AF start date??

Sally 💙💗💗💗

This might be a dumb question, but my husband and I decided 2-3 weeks ago to start TTC. I starting logging my cycle dates, but I'm confused when I should have as the actual start date. I stared spotting Wednesday evening before bed and woke up Thursday morning with full on period. What date should I put as the start? Wednesday or Thursday? Anyone's input would be appreciated!