Topping my list of Microsoft Excel pet peeves is the program's automatic conversion of two numbers on either side of a hyphen into the date and month the numbers correspond to, such as "1-1" becoming "01-Jan."
The change occurs even when you choose any of the options available when you select Paste Special. I have looked high and low for a way to disable this setting in Excel, to no avail.
You can make the change for an entire worksheet by clicking the small box above 1 and to the left of A in the top-left corner, or by pressing Ctrl-A or Command-A to select all the sheet's cells. Then right-click any cell, choose Format Cells, and select Text in the left pane under the Number tab.
There's also a one-keystroke solution: type an apostrophe before entering or pasting a pair of numbers that Excel could mistake for a date and month. When you exit the cell, the apostrophe vanishes and the numbers stay numbers, formatted as text.