Weeks in a year calculation
One year has approximately 52 weeks.
Weeks in a common Year
One calendar common year has 365 days:
1 common year = 365 days = (365 days) / (7 days/week) = 52.143 weeks = 52 weeks + 1 day
Weeks in a leap year
One calendar leap year occures every 4 years, except for years that are divisable by 100 and not divisable by 400.
One calendar leap year has 366 days, when February has 29 days:
1 leap year = 366 days = (366 days) / (7 days/week) = 52.286 weeks = 52 weeks + 2 days