I watched a reality show last night and the characters were toasting saying 'for the past, present and beyond'
I wonder why they said 'past, present and beyond' instead of 'past, present and future'.
Is it a kind of idiom?
If you don't know by now, I'll tell you: 'Reality' shows are anything but reality. Nothing done or said is unrehearsed or unwritten. Writing for television has little connection with proper English grammar.
As to this 'toast', you were pretty close with your guess at idiom. Change the letter m to a t and you've got it...