This will cause Excel to display the year and month together, but will not change the underlying date.
in a text string with the number format of your choice.
Convert date to month and year
To convert a normal Excel date into yyyymm format (e.g. 9/1/2017 > 201709), you can use the TEXT function. In the example shown, the formula in C6 is: =TEXT(B6,"yyyymm")
