Date Functions and reference

= DateAdd(DateTime.Date(DateTime.LocalNow()), 6, MONTH)
OR
= DATEADD(DateTime.Date(DateTime.LocalNow()), 6, MONTH)

Expression error: The name 'DateAdd' wasn't recognized. Make sure it's spelled correctly.

Also, Can someone pls share a functions reference link so that I can bounce myself over it before I post basic questions

Thanks for the replies.