The general Watchathon may or may not happen this year. There is another thread about it. Last year was a snoozer, with little available. I think this year may not happen at all.
The movie channels sometimes have free OnDemand at times. Comcast rarely, if ever, mentions it. You need to keep up on Press Releases from the networks, and even then, Comcast may or may not participate.
You can stream and on demand cinemax and HBO this weekend man.
that's how it works but the linear channels don't work OH BOTHER>
Watchathon, Xfinity's biggest week of FREE television, will begin on Monday, 04/16/2018, and will run until Sunday, 04/22/18. For more information on how to view all the available content, please see here: https://forums.xfinity.com/t5/Channels-and-Programming/Xfinity-Watchathon-2018/m-p/3071142
After Watchathon is complete, you will be able to find any free previews posted on our Channels and Programming board when they run.