robertsconley
Should be playing D&D instead
It only matters if the players have a reasonable chance of affecting one another. Generally, it works out that simultaneous campaigns are set in different regions of the Majestic Wilderlands. One group is adventuring in the City-State of the Invincible Overlord and the other is in Viridstan. Even when in the same region the two groups are often in different social or cultural circles so their chances of interaction are low.
The nice thing is I don't have to metagame this. I just do my usual thing of saying "Here are some places to adventure in, some situations for characters to deal with. Which one do you want to try for this campaign?". It is rare that the two different groups pick something where I would have to track time strictly. But I do always keep track of the calendar.
Later when their characters are most established and capable of having a wider impact (i.e. wealth, power, at an Olympic caliber level of experience, etc.) interaction between different groups is more common but still rare. And since the late 90s easily handled by getting the involved folks connected via email or posts rather than having them show up at a session. Prior to that I would ask for instructions from the involved parties independently along with passing along any letters or notes.
I never had a situation where I was located at a place (house or game store) and had to track multiple groups doing their own thing. The closest was running various game store campaigns. And most of the time it worked out that a plausible reason could be created why a character wasn't there one week but not the next. For example, if the party was exploring a vast dungeon, like Tegal Manor, the missing character left and returned to the party's camp.
After playing a lot of live-action roleplaying in the 90s and running buffer LARP events, I experienced firsthand what would happen if you had dozens of adventurers milling around all doing their own thing and pursuing their own agenda. As much of a genius Gygax was, the whole keep strict time record business doesn't really do the job compared to how it really works. So like any good referee, I use that experience in my tabletop to play things by ear to create enough verisimilitude to make the experience feel right when it pertains to time, and characters dropping in and out.
