Date being replaced by text in monthly financial period but still acting as a date

Hello,

Quick question, hopefully this doesn't require VBA.

In my spreadsheet attached, look at cell K5 (highlighted in yellow)
Instead of entering the month, I'd like to be able to enter P1, P2 or whatever period up to P12 instead of the date BUT the calculations would still happen as if it was a date in K5. (even better if I can put it in a dropdown list)

Mar-2024 represents P1
Apr-2024 represents P2
May-2024 represents P3 and so on
.
.
Feb-2025 represents P12

Thank you for your help.
Pat