Hi @john john Pter,
Thank you for posting in this community.
I tested your formula in my environment but I was able to save it successfully. There is no problem with your formula.
But I ran into another issue where the calculated column doesn't show up in the list even though it calculates the value of the date.
This is most likely an issue that arose with a recent update to SharePoint, so I suggest you open a ticket for it.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.