samsung 816 changing from 24 too 12 hour clock - Sundance Business VOIP Telephone Help

I can't find the code to change from 24 hour too 12 hour clock samsung prostar 816. Doses anyone still rember it?

The book says to dial #20 1,2,3,4 and then 4 for 12 hour or 5 for 24 hour.

Thank You that is the last 816 I have out there and I throw out my books a few months ago Thanks Again