Any month of the year can have either four or five of any day of the week. The only exception is February of a non-leap year, which always has four of every day of the week.
A 31-day month that begins on a Wednesday, Thursday or Friday has five Fridays. A 31-day month that begins on a Sunday, Monday, Tuesday or Saturday has four Fridays.
Examples:
There are 5 Fridays in December.
There are 53 Fridays in 2010, the last one of which falls on December 31, 2010.
Both dates are Fridays, and including both there are 41 Fridays.
In 2011, the months that have 5 Fridays are; April, July, September and December.
There will be 52 Fridays in 2020.There will be 52 Fridays in 2020.There will be 52 Fridays in 2020.There will be 52 Fridays in 2020.There will be 52 Fridays in 2020.There will be 52 Fridays in 2020.There will be 52 Fridays in 2020.There will be 52 Fridays in 2020.There will be 52 Fridays in 2020.There will be 52 Fridays in 2020.There will be 52 Fridays in 2020.
52 Fridays
There were 52 Fridays in 2007
In 2005, there were 52 Fridays.
In 2009, there were 52 Fridays.
There are 52 Fridays in 2012.
There were 52 Fridays in 2014.
Exactly 14% of all Decembers have five of each of Fridays, Saturdays and Sundays.