Since there is not a built in "geometric mean if" function, here's how I would probably do it:

1) Create a helper column. Because the built in =GEOMEAN() function will ignore text values, I would use a function in this helper column that would return a text string (like "" or other) for those values that did not meet "criteria". Something like =IF(A2=date,B2,"notused") where date refers to a cell that contains the date of interest.
2) Then, another cell could be added with the built in GEOMEAN() function. =GEOMEAN(F2:F22), assuming F contained the helper column.

There are a lot of different variations around that kind of theme, so figure out the details of how you would like to do it, but that is the basic approach I would use.

Help file for GEOMEAN() https://support.office.com/en-us/art...3-0b38980e40d5