People clock

We watched a photographer and his assistants corral passers-by into being shot for a people clock in Daikanyama.
It wasn't strictly a bijin tokei, or "beautiful lady" clock, but it was the same idea. There were couples, people with babies, and groups of three each taking a turn holding a pink erasable board with a different time on it.
We were sitting on the terrace at a cafe called Sign. They packed up and left before we were done, and I didn't get to ask what they were shooting for. The most obvious assumption would be that it's for an iPhone app. Whatever it is, I heard the photographer tell one of the sign-holders that it would "start on April first."