I've seen people say that before. I've had it not work less than a dozen times and have used the ability across 3 of 4 accounts almost weekly throughout D1 from a week after matchmaking in Strikes was introduced until I stopped playing a few months prior to D2 dropping. Run the same way on one account throughout the run of D2 from 3 to 5 days per week. Some of those times that it failed were early on and I was having to figure out what I had done wrong while a few others failed when I started running with another person and the wrong person (not the host) did the time change. You have to be the host and you can't simply change the date then immediately go into strikes or down to a planet and expect it to work. I generally set the date while in orbit, wait a minute and go down to the tower. In the rare event that I am met with other players at the tower then I go back to orbit and back down to the tower. Not once have I had it fail to work on the second trip down to the tower unless I have set it up incorrectly. I also don't change just a few hours or even just a few days. I set the date back by years (and a lot of them). I don't know what the case is for why you are unable to get it to work but once I figured out the host deal with my friend and I then I have not had it fail a single time since then and that has been over 2 years now. Also you can't start the game with the date changed or it will simply match like normal until you reset the date to current, go into an activity/planet/tower, go back to orbit and then change the date back. There are variations (like setting the date back while already in an activity) but I have always found it best and easiest to explain just to start the process in orbit. Considering I travel, use multiple consoles (2 at home and one in my travel rig) and a variety of internets (due to traveling for work), I can definitely say it's not simply my setup and/or luck. It just works.