lunchthirty
Past lunchtime....or....a latish lunch
"Dude, I gotta go, it's lunchthirty" ("Gotta go, It's past my lunchtime!")
or
"So we'll meet you guys at Joe Schmoe's Bar & Grill around lunchthirty on Friday?" ("we'll meet for a late lunch at Joe's?")
or
"So we'll meet you guys at Joe Schmoe's Bar & Grill around lunchthirty on Friday?" ("we'll meet for a late lunch at Joe's?")