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How many weeks in a year ?
A normal year in the 'modern' calendar has 365 days, which, when divided by 7 (Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday) equals 52.1428571 weeks. Every four years, there is a leap year*, adding an extra day into the calendar (pity those 17 year olds born on February 29th 2000, who have only had 4 true birthdays). In this case, the calculation is 366 divided by 7, which equals 52.2857, so it's still just 52 weeks. This is all based upon the Gregorian calendar (introduced back in 1582), which cycles every 400 years. If you want to go a step further and work out the average number of weeks in a year across the full Gregorian calendar, you'll find that a year works out at 365.2425 days. When divided by 7 it gives you a total of 52.1775 weeks.