From the Statements received, we see that only the Month and Year is present as a text format, so the information on the day is not present, hence we will take it as current date’s day value.
So, we would require to convert it to a Date value at first then register/enter it into the Excel sheet and then use Format Cells activity to format it to the required format.
There is a difference in the original date value format, however it is understood as date value.
An Initial analysis could be done by checking the Other Excel related activities present. There is a For Each Excel sheet activity which should work with the current configuration set up in the workflow.