The time of day when two or more stoners (i.e. daily marijuana users) get blunted. It's optimal usage answers the question "what time is it?" to signal that persons readiness to get high.
Stoner 1: Dude, I gotta take a huge dump, get fresh, eat lunch and be at work soon. What time is it?
Stoner 2: (simulates reading of wristwatch) My watch is saying blunt:30, bro.