Average Elapsed Time With Conditions Using Dates & Numbers

Dataset is 220K rows. A small subset follows.

Using an array calc with criterions Day = 1 and Hour = 1 summed on Elapsed Time returns 81 with an average of 11.57 for 7 events of which there are 5 distinct dates.

The function =SUM(IF(D2:D14<>"",1/COUNTIF(D2:D14,D2:D14))) returns the number of distinct dates in the dataset ie 7.

Is it possible to combine these two methods to create an average of elapsed time by day and hour using a denominator of distinct dates for only that combination of dimensions?

I have attempted to calculate an item in a pivot table using a different denominator without success.

day Hour Date Elapsed Time
1 0 5/03/2009 25
1 0 5/03/2009 24
1 1 5/03/2009 23
1 1 7/03/2009 11
1 0 7/03/2009 5
1 1 8/03/2009 2
1 1 8/03/2009 8
1 1 9/03/2009 4
1 1 9/03/2009 17
1 0 9/03/2009 22
1 1 10/03/2009 16
1 2 13/03/2009 12
2 1 14/03/2009 15