If you're entering the week-ending date in each cell, you can enter it
in one cell and have the others refer to the first cell.

Say you have your week-ending date in cell A1 on a sheet called Data.
Change that cell. All other cells on the same sheet that need to show
the same date would have the formula:

=A1

All cells on other sheets needing to show that date would have the
formula:

=Data!A1

So when you change A1 on the Data sheet, all the other week-ending
dates change as well.