# Count dates by day of week

=SUMPRODUCT(--(WEEKDAY(dates)=day_num))

To count dates by weekday (i.e. count Mondays, Tuesdays, Wednesdays, etc.), you can use the SUMPRODUCT function together with the WEEKDAY function. In the example shown, the formula in F4 is:

=SUMPRODUCT(--(WEEKDAY(dates,2)=E4))

*Note: "dates" is the named range B4:B15.*

You might wonder why we aren't using COUNTIF or COUNTIFs? These functions seem like the obvious solution. However, without adding a helper column that contains a weekday value, there is no way to create a criteria for COUNTIF to count weekdays in a range of dates.

Instead, we use the versatile SUMPRODUCT function, which handles arrays gracefully without the need to use Control + Shift + Enter.

We are using SUMPRODUCT with just one argument, which consists of this expression:

--(WEEKDAY(dates,2)=E4)

Working from the inside out, the WEEKDAY function is configured with the optional argument 2, which causes it to return numbers 1-7 for the days Monday-Sunday, respectively. This makes it easier to list the days in order with the numbers in column E in sequence.

WEEKDAY then evaluates each date in the named range "dates" and returns a number. The result is an array like this:

{1;3;7;1;5;2;7;1;7;5;4;7}

The numbers returned by WEEKDAY are then compared to the value in E4, which is 1:

{1;3;7;1;5;2;7;1;7;5;4;7}=1

The result is an array of TRUE/FALSE values.

{TRUE;FALSE;FALSE;TRUE;FALSE;FALSE;FALSE;TRUE;FALSE;FALSE;FALSE;FALSE}

SUMPRODUCT only works with numbers (not text or booleans) so we use the double-negative to coerce the TRUE/FALSE values to one's and zeros:

{1;0;0;1;0;0;0;1;0;0;0;0}

With a single array to process, SUMPRODUCT sums the items and returns the result, 3.

### Dealing with blank dates

If you have blank cells in the list of dates, you will get incorrect results, since the WEEKDAY function will return a result even when there is no date. To handle empty cells, you can adjust the formula as follows:

=SUMPRODUCT((WEEKDAY(dates,2)=E4)*(dates<>""))

Multiplying by the expression (dates<>"") is one way to cancel out empty cells.

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