They are just 'natural' time periods. The Earth orbits the sun once a year. The moon orbits the Earth roughly once a month, and the Earth turns on its axis once a day !
500 years is about 182,622.5 days.
There are 30,660 days in 84 years (84 years x 365 days/year).
28 days = about 0.077 years.
There are 3,285 days in 9 years ----- 3287.1797 days in 9 years
2 years and 316 days.
1 years and 151 days.
2 years and 69 days
4 years and 14 days.
1 years and 151 days.
If neither years is a leap year, 735 days = 2 years, 5 days. If either is a leap year, it is 2 years, 4 days.
== == 20 years = 7,304.84398 days Use google "Convert 20 years to days"
27 years, 4 months, 15 days.