When I first joined ADISC the first time several years ago, I remember seeing the suggested 'rules' for SIDF, so I have had a search and found this comprehensive synopsis posted in by an ADISC member way back in 2012. As a reminder, I hope they don't mind me re-posting them - here goes:
Sleep In Diapers Friday
An ADISC Tradition
ADISC has been around for a number of years now, and over this time, we have established a number of community traditions. Perhaps none of these are as often thought of or as notable as Sleep In Diapers Friday (or SIDF).
What is Sleep In Diapers Friday?
This monthly 'holiday' just happens to have a very self-explanatory name! Basically, it's a night that members of the greater ADISC community come together and indulge in the reason they came to this site in the first place. We put on a diaper and fall asleep. It's that simple!
When is Sleep In Diapers Friday?
The first Friday of every month. That's right, the
first Friday, not every Friday. Not everyone here wears diapers every night, so doing it every week would be overkill. Holding it once a month makes it more special and keeps it as something for people to plan for.
Are there any incentives in participating?
Of course there are. You're sleeping in a diaper! What more could you want?
Seriously though, there aren't really any on-site advantages to taking part in a Sleep In Diapers Friday, but it is always a fun thing to do.
If you are interested in putting a number on things, you can feel free to try out:
SIDF Points
Some time ago, a member posted a 'Rewards Program' for participating in Sleep In Diapers Friday. While there is no real reward in getting these points, the satisfaction that comes in the act of gaining them can be quite fun!
Brief overview
There are a total of 5 SIDF Points that can be earned each time SIDF comes around. Here are the points you can win.
Point 1
Get the date right! SIDF begins before midnight (24:00 or 12:00AM) Friday night/Saturday morning in your timezone. If it's not SIDF, you shouldn't be getting any of these made up points, though you still get the enjoyment of sleeping in a diaper anyways!
Point 2
Wear a diaper! It doesn't matter what kind of a diaper it is; just wear some sort of a diaper on SIDF night to earn this point.
Point 3
Leave the diaper on for the duration of the night. This means using it as it was intended to be used. If you need to change and have another diaper you can use, change into it to keep up with this point! (Note: feel free to follow your usual routine for messing without penalty).
Point 4
Sleep! This isn't Stay Up In Diapers Friday! Get the fourth point for actually sleeping a decent night's sleep on SIDF. For those new and having trouble falling sleeping in diapers, this gets easier as time goes on.
Point 5
Have fun and enjoy being diapered! This is a time to get in touch with the diaper loving and/or regressive side of you and to indulge in your interest, no matter how often you get to.
So, that's it. If you wear a diaper, use it for its intended purpose, sleep, and have fun on an SIDF night, it's a free and totally worthless 5 SIDF Points for you!
A big thanks for this original 2012 overview of SIDF and have fun! 
