It's a sign!

Literally, a sign... Not cryptically or anything, the green masked stalker is back and this time he was standing on the conservatory roof, I'm not sure how he didn't fall through because even a feather would make that thing crash and burn to the ground... And he knocked on the window holding up a sign saying "29/7/94"

What's this all about? What's 29/7/94? Anyone know of anything relating to this?! Let me know...

~Dan