No, 90 days is 3 months. A year and 3 months is 15 months or 450 days (using 30 days as a month).
Use 365 days for the number of days in a year
1/3 of a year is 120 days.
A fraction requires two numbers. 21 days as a fraction of what? A month, a year, a century?
45 days is approximately 1/8 of a year.
Assuming it is a normal year with 365 days, the fraction would be 65/365 = 13/73
about 16.4%
90% of sunshine/year = 328.5 days/year
In a regular year, adding 90 days to January 28 gives April 28. In a leap year, adding 90 days to January 28 gives April 27.
Adding 90 days to October 16 of any year gives January 14 of the following year. For example, 90 days on from October 16, 2010 is January 14, 2011.
Adding 90 days to November 29 of any year gives February 27 of the following year.
Adding 90 days to December 23 heading into a non-leap year, gives March 23 of the following year. Adding 90 days to December 23 heading into a leap year, gives March 22 of the following year.