Timer / Arrow Signs?

Molduga

I've been seeing these strange signs with timers on them, and some others that can make an arrow image when viewed. Can someone please explain to me on how to get/code them?

LittleDuneBuggy

I have no idea how to do it, and nobody that I've asked has told me, but I suspect it uses hashtags, because of the farmers almanac.

U

This is a game exploit that you could get into trouble for recreating. I am going to close this thread.