Calculating the average elapsed time in Excel 2010

In our sql server table, we have a field of type DATETIME. This field is populated by a vendor product with the elapsed time of an event.

We created a SQL Server view of this column and other columns of info joined together from several tables.

Then we create in Excel 2010 a new spreadsheet with a data connection to the SQL Server, instance, and view that we created.

Excel 2010 displays each of the columns in our view.

The elapsed time column appears as "dd hh:mm:ss". However, when we click on a cell to look at its formatting, Excel lists it as general.

We want to calculate the average time in this column.

We go down below the data, click on a cell, and insert =Average(C2:C17215) and we get an error saying dividing by zero.
That's nonsense - we have 17,000+ rows of data, so there is no divide by zero math going on here.
Each row in this column has data, so there are no blank cells.

We have spent some time web searching. We then tried various methods of calculating this. Nothing has worked. In most cases, we get the divide by zero. We tried some solutions that mention using an array forumula, but that just changed the error to an invalid value error.

This seems like such a common thing that people would want to do, we must be missing something simple.

Does anyone have any insights on what we are missing in getting this to work?

Thank you.