Girls when is your first period?

I can vividly remember when I had my first period because I was in school celebrating teacher's day. It was 31st August 2007, I was 12 3/4 at that time. I remember having so much pain, I thought it would go away but it didn't. When I went home my mom saw my underwear covered in blood, and she was so surprised, and she said "Oh my god you had your first period!" And I was like convincing her no, no, no. Lol it was pretty funny and scary at the same time.