In the Gregorian calendar, every year which is divisible by $4$ is a leap year, except for years which are divisible by $100$; those years are only leap years if they're divisible by $400$. (This may seem complicated, but the calendar is carefully designed to keep the average number of days per year very close to the number of days in one complete orbit of the Earth.) Assuming we keep using the Gregorian calendar, how many leap years will there be between $2001$ and $2999$?