The birthday of the mouse is on its registration date!
An birthday hat icon will appear next to the username on the mouse's profile when it's his/her birthday.
Warning: Those are not the birthdays of the mentioned mice, just used as an example.

If you tried to click on the birthday hat, a tab will appear. It contains the birthdays on the same date (common birthdays).

Some people see this pointless, and maybe they think it's actually stupid.
It's actually a great way to remember when you used to be a normal mouse and a rookie, and remember to celebrate your mouse birthday with your friends!


Extra:

When it's your birthday, a birthday hat icon will appear next to your name.


Thank you for reading.