Grammar help

[kirkandpetal]

I'm making a sign for a party that says

Kate's 40th

Is is Kate's with or with an apostrophe?

Having a sudden lack in my my judgement!!

That should be "with or without"

With an apostrophe

With

It’s Kate’s 40th as the 40th belongs to Kate!

With - the 40th belongs to Kate.

Thanks - that's what I thought but after drawing it out and looking it for ages (it's a complex signage take) I started to doubt myself.

Thanks again!