Subtract 30 minutes from a Hour Column using forumla

Im trying to set up an automated schedule creator.

At the moment I have the Parent item being created and then User inputting a time using an hour column.

From that im trying to use a formula to subtract 30 minutes from that.

I cant work out a forumla that will work

I tested this, I don’t believe it is possible…

I keep getting results like this:
Screenshot 2024-04-01 162127

Also, when I change the hour, it changes the day, month, and even year the formula spits out!

This is really strange, and I’m sorry I couldn’t answer your question.

Hope you are able to solve the issue!

Edit: Attached the wrong image, fixed it

Yep I had the same weird formatting and wrong answers. Ive pivotted to using a Date column and running this formula:

FORMAT_DATE(SUBTRACT_MINUTES({Take Off Broome}, 30), “HH:mm”)

Which works but would have preferred to use an hour column as the parent column not a date column as the it will take more time to set the time

I see… Interesting fix!

I’m glad you found a solution that works, sorry I couldn’t help.

I actually may use this solution in the future if I need it! Thanks for sharing here!