( by Davis Daniel )
Have a look at the following screenshot of "Sheet2":
In the above sheet I have the following formula in Cell A1:
=query('Sheet1'!A:N;"select A,sum(N) where A is not null group by A label A 'Date', sum(N) 'Total Hours' ";1)
In the above formula change "Sheet1" to the name of the sheet in which you have the data.