Cycle day confusion;

Hey girls,

Just wanting to see people opinions and when they count there first day of there cycle, do you count day 1 the moment you see blood as of spotting, light bleeding, or when it’s a full blown period?

I only ask because I started my period at 10;30 at night on the 15th, but don’t know if that’s day one or if the next day would start as day one since the 15th was already almost over? Can I have people’s thoughts please. 😂