Well there are 365 days in that year and January 1st is on a Friday so that will be the beginning of every week for 52 weeks + 1 day (52 x 7 = 364 + 1 = 365) and that one day will be a Friday.
So if...
A month always has 28 or more days, so as there are 7 days in a week there are always at least 4 Saturdays and four Sundays in a month. As most months have more than 28 days, there can be up to 5...