When do you log you're period starting?

Hi,

I'm new here. Me and my husband have decided to starting trying in October so I'm starting to learn the basics now. I'm curious when you put that your period is starting. Do you do it as soon as you start seeing blood? Or do you put your first day when there is enough blood that you need a tampon or pad? I normally have a couple days that it's really light and it's not heavy enough to wear a pad or tampon. So I'm confused on what's considered the first day of your period. Thanks for the info.