10-4
Over and Out Day gives you a time to use a two-way radio to sign off. You don't have to sign on or even have a real conversation with anyone. Just get connected and then say, "Over and out."
Another possibility for celebrating this day has nothing to do with radios.
You could go over the top of something - anything - and then get out of something - again, anything.
For example, you could go over hill and dale followed by going out to eat.
You could go over the top, semantically, and then go out on the town.
You could fall over and then get out of town.
The possibilities are limited only by your imagination and the meanings of "over" and "out".
When you get tired of doing over and out activities, you can switch to 10-4, which is essentially the same thing only less so.
Written as it is above, you could translate this to 6 day, since 10-4=6.