You can't wear a tank top two days in a row, and you can only wear your hair in a ponytail once a week. So I guess you picked today.
10 seconds sound clip from the Mean Girls (2004) movie soundboard.
You can hear this line at 00:13:45 in the Blu-ray version of the movie.
Quote context
[...]
- Fine.
- No.
- And we only wear jeans or track pants on Fridays.
- Okay, like, if I was wearing jeans today, I would be sitting over there with the art freaks.
- I mean, you wouldn't buy a skirt without asking your friends first if it looks good on you.
[...]