Spreadsheet: How many days in first and last week of a month?

[Drumdevil]

Hi everyone,

I am looking for two spreadsheet formulas (Google drive/MS Excel) that counts the number of days, in the first or last week of any given month.
It is for a financial sheet, where weekly budgets are given. Every month starts on the same day (23rd).

I'd like to calculate the budget of the first and last week by dividing it by 7, and then multiply it by the number of days the first week or last week has.

Can anyone help me with that?

Thanks in advance.

[editline]21st June 2014[/editline]

Already figured it out using "=weekday".