When is Day 1?

For as long as I can remember, my period has started with spotting and light bleeding, followed by heavier bleeding. Since I went off birth control a few months ago, I seem to have two days of spotting and light bleeding before I get the heavier flow. What do I count as day one? I’ve seen some professional websites that say the first day of the regular flow is day one, but others say to count the day I spot as day one as long as it goes right into my period without a day or so in between.