How to count number unique names in one column where there is a specific date in 2nd column

JennyMarfell-Jones To return a distinct count of server names for a specified date, the SUM / COUNTIFS method can be used with the UNIQUE function (Excel 2021 or later). For example, if the input cell for the specified date is cell D2, the following formula can be used:

=SUM(IF(COUNTIFS(B2:B13, D2, A2:A13, UNIQUE(A2:A13)), 1))

COUNTIFS Distinct Count

With Excel for MS365 (or Excel for the Web), you can also create a summary report for all dates in the dataset using the HSTACK and BYROW functions:

=LET(arr, UNIQUE(B2:B13),
HSTACK(arr, BYROW(arr, LAMBDA(r,
   SUM(IF(COUNTIFS(B2:B13, r, A2:A13, UNIQUE(A2:A13)), 1))))))

Alternatively, the ROWS / FILTER method can be used for a specified date:

=LET(data, UNIQUE(A2:B13), incl, DROP(data,, 1)=D2,
IF(OR(incl), ROWS(FILTER(data, incl)), 0))

Or, to create a summary report for all dates in the dataset:

=LET(a, UNIQUE(A2:B13), b, DROP(a,, 1), c, UNIQUE(b),
HSTACK(c, BYROW(c, LAMBDA(r, ROWS(FILTER(a, b=r))))))

Please see the attached workbook, which contains all of the examples shown above...