In working on the Resident Adviser Duty Schedule spreadsheets for Housing and Residence Life, we changed the procedure a little bit. Instead of having 20 individual spreadsheet files with 10 sheets in them for each of the months, we made 10 monthly spreadsheets with 20+ building sheets in them. It allows us to make changes to one master file for the month, and it is referenced by all the building sheets. Using Office 365 we can have 20+ users making schedule updates at the same time without locking the sheet.
You can imagine that formatting and copying and pasting formulae across 20 sheets could be a nightmare, but Excel has that covered for us, and has a way for us to make changes across multiple sheets.
Making changes in multiple sheets
You can select multiple sheets at one time by holding down the Ctrl key as you select the sheets you need to modify. Making a change on the current sheet will then replicate across them all.
If you want to change all the sheets at once then right click one of the sheet tabs and choose Select All Sheets.
Using some of these features in Excel can save us an immense amount of time. Let me know in the comments which features you use most often.