So you did a great thing posting a sample data set so I could play with it during lunch.
Attached you will find what you are looking for.
TimeSheet.xlsb
I added a ton of comments to the code so you can see what I am doing for each line.
A few notes:
1) You really don’t NEED VBA to create the aggregated data, you could just copy and paste the 12 tabs into ONE data tab
2) At this point the Pivot Table will do everything else, and if you don’t know pivot tables you NEED to learn them as they are SLIIICK and probably one of the most powerful tools in EXCEL
3) Also they are VERY easy to use, once you have standardized data like you have 
4) Then I took this one step further and made a dynamic named range for you called PivotDATA
4a)PivotData counts the number of rows used in column A then counts the numbers of columns used in Row 1, and adjusts to perfectly match that, so as you increase or decrease in size it will automatically adjust
5)SO now that you have the VBA to copy and paste, the formula to dynamically adjust the pivot range, AND the pivot table you never need to do anything but enter data.
6)Impress Boss and Prosper.
If you have any questions just ask.
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