Event @pings with an End Time

The end of an event turns off my @everyone or @johnsmith pings. 
So I can set up a ping with a 3 hour timer.  Or ping that ends at a set time. 
Now people who log onto Discord after the event has finished will not see the ping. 
Ping @everyone to watch tonights Luna Eclipse.  With an end-time people will not be pinged after it's over.