There are approximately 52 weeks in a common year. A common year has 365 days, which when divided by 7 (days per week) results in 52 weeks and 1 extra day. In a leap year, which has 366 days, there are 52 weeks and 2 extra days. This is because the calendar year is not an exact multiple of weeks, so the extra days account for this discrepancy.

Summary:

• Common year (365 days) = 52 weeks + 1 day
• Leap year (366 days) = 52 weeks + 2 days

So, generally, a year contains 52 full weeks plus either 1 or 2 additional days depending on whether it is a common or leap year.