This macro put the current day into a cell but it can put also the day of the previous or next month. Also, I put another macro doing the same thing except that it will personalize the format. The first one will only use the default format.

When I use the macro ?

To put the current day, for instance, to know the last day that the file was opened.

How to create the macro ?

Read How to create, edit, hide and select a macro in an excel report

How to create the button to associate it with the macro ?

Read How to create a button and associated it to a macro in an excel report

How is the macro ?

Copy the code below and paste it into your macro. You will see my comments in green if exist so follow the help to adapt to your need.

Put the date without customized format:

Sub test()
' changeB2 by your cell
' change 0 by -1 for previous month or 1 for next month
Range("B2") = DateAdd("m", 0, Date)
End Sub

Put the date with customized format:

Sub test()
' change B2 by your cell
' change 0 by -1 for previous month or 1 for next month
' changedd-mm-yyyy by what you want for instance dd/mm/yyyy
Range("B2") = Format(DateAdd("m", 0, Date), "dd-mm-yyyy")
End Sub