Drown Down List on Multiple Sheets

Hi,
I have a an excel file with a sheet that has a drop down list of Months at the top. When you change the month, the sheet repopulates.

I want to add 2 more sheets to this file with the same drop down list. I want the drop down to be the same on all sheets AND I want it so that you can change it on any sheet! IE, If i am on sheet one viewing January, all 3 sheets say January. If I go to sheet 2 and change it from January to February, I want all 3 sheets to change to February.

I tried searching and the closest I found is just having an =Sheet! reference but that does not let me change the drop down on any sheet, only the first.

So in short:
Need identical drop down list on all sheets
Need to be able to change drop down on every sheet and have it change on every sheet.

Many Thanks!

I need to have the tabs separated as they have different accounts and one takes into account the number of working days while the other takes into account the monthly headcount.