Explanation
First, this formula determines a "start date". The "first of month" is calculated with the DAY function here:
=B5-DAY(B5)+1
Then n * 7 days is added the first of the month, to get a start date n weeks from the first of the month. In the generic form of the formula, n represents "nth".
The next step is to calculate the adjustment required to reach the final result. The adjustment is calculated using WEEKDAY and DAY:
WEEKDAY(B5-DAY(B5)+8-C5)
Inside WEEKDAY, the first of the month is again calculated, then 8 days are added and the value for dow (day of week) is subtracted. Day of week is abbreviated "dow" in the generic form of the formula. This is a number between 1 (Sunday) and 7 (Saturday) which can be changed as needed.
Finally the calculated adjustment is subtracted from original start date to get the final result.
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Get last working day in month
Get last weekday in month
Related functions
DAY Function
The Excel DAY function returns the day of the month as a number between 1 and 31 based on a given date. You can use the DAY function to extract a day number from a date into a cell. You can also use the DAY function to extract and feed a day value into another function, like the...
WEEKDAY Function
The Excel WEEKDAY function takes a date and returns a number between 1-7 representing the day of week. By default, WEEKDAY returns 1 for Sunday and 7 for Saturday, but this is configurable. You can use the WEEKDAY function inside other formulas to check the day of week.
