What is considered first day of period?

So whatvis considered the first day of your period? Is the first sign of blood? Three days ago I had a light pink color when wiping. Then it turned into some spotting the next two days by the end of last night no spotting and this morning nothing again. My period was kind of like thisn ast month too. I spotted a few days and then I could definitely tell my period started. When recording on glow do I say period started the 24th or wherever bright red bleeding begins.