A Federal Government website managed by the U.S. Department of Health and Human Services. healthfinder.gov is sponsored by the National Health Information Center 200 Independence Avenue, S.W., Washington, DC 20201 Page last updated: Thursday, April 20, 2017.
Assuming a 90 year spell includes 22 leap years, the number of days is equal to (68 x 365) + (22 x 366) = 24820 + 8052 = 32872 days. If the 90 year spell includes 23 leap years, the number of days is equal to (67 x 365) + (23 x 366) = 24455 + 8418 = 32873 days. 3 people found this useful.
However, there is one exception to the leap year rule involving century years, like the year 1900. Since the year is slightly less than 365.25 days long, adding an extra day every 4 years results in about 3 extra days being added over a period of 400 years.