# Interesting numbers related to time ## Things that are always true - 24 hours in a day - 60 minutes per hour - 60 seconds per minute - 3600 seconds per hour - 31 days for January, March, May, July, August, October, December - 30 days for April, June, September, November - 28 or 29 (leap year) for February ## Stuff that are mostly true - The number of day in a year - 365 days in a normal year and - 366 days in a [leap year](https://en.wikipedia.org/wiki/Leap_year) - 8760 hours in a normal year - 8, 7, 6 <- easy to remember :) - 8784 hours in a leap year ## Stuff that is a useful approximation - [[why 730 hours|730 hours]] per month on average (for a 365 days year) - 52 weeks per year, the real value is - 52 weeks + 1 day for non-leap years - 52 weeks + 2 days for leap years ## Hours Hours in the day: 24 Hours in a month: - 720 for 30 days - 744 for 31 days - 696 for 29 days - 672 for 28 days ## Days - 31 days for January, March, May, July, August, October, December - 30 days for April, June, September, November - 28 or 29 for February # Excel formula ## Number of days in a month A1 contains a date, EOMONTH returns the last day of a month, DAY return the day (1..31 of the date). Smart ```Excel =DAY(EOMONTH(A1,0)) ```