Whats it called when a parent is ie 30 and when #s reversed are their childs age ie 3?

I know its not a Sunshine birthday which is your age matching the month date you were born ie age 28 and born March 28th. I can't seem to find anything on the internet - PLEASE HELP

Whats it called when a parent is ie 30 and when #s reversed are their childs age ie 3?windows xp pro

You have a great party.