Ctrl-click several tabs and they're grouped: anything you type, format or delete happens on every one of them, in the same cell. For twelve identically-laid-out monthly sheets that turns an hour into a minute. It is also the most dangerous state in Excel, because the only indication is the word [Group] in the title bar and slightly different-looking tabs — and if you forget, the next thing you type overwrites eleven other sheets silently. Make ungrouping the reflex: the moment the edit is done, click a tab outside the group.

1. 1Click the first tab, then Ctrl + click each other one. Right-click → Select All Sheets groups everything.
2. 2Make the edit once. It lands on every grouped sheet in the same cell.
3. 3UNGROUP immediately — click any tab outside the group, or right-click → Ungroup Sheets.

Press the shortcut to play it on a sample sheet.

• Fix a heading or a formula across every month at once.
• Apply the same print setup to a whole workbook.
• Set up twelve new monthly tabs identically in one pass.