Time tracking is one of those things that while everyone is kind of aware of it, often doesn't get tracked too closely in my experience. We're all aware that the group has spent "about a week" or whatever traveling. We know that we've taken X long rests in the dungeon, meaning we've been there at least that many days. But what does that all add up to? And do you track it?
Currently I'm running two D&D games. In one of them I set up a full calendar for the year - complete with a lunar cycle to go with it. Donjon helped a lot with that, and I made some choices to make it easier. The moon is on a 20 day cycle. Weeks are 10 days. You get 4 weeks to a month, and 10 months to a year. This means 2 lunar cycles per month, and 400 days to a year.
This additional 40 days per year gives a not insignificant extension to the lifespans of the races, but that's mostly not here nor there.
The interesting thing though has been that in the game I'm tracking more closely, I find myself surprised at times both at how much time has passed, and how little time has passed. We've done two to three sessions that were all in the same 1-2 day period of time. At the same time, we've had sessions lop months off the calendar as the group traveled, waited, or did other things.
The better part though is since I know I am tracking time, I've been able to use it to plan out certain events. "Bad guys" have significant things happening at set dates that are coming up. Potential interruptions to the PCs plans are scheduled. When we get to those dates, those events can happen, and the PCs will have to choose. For me it is as simple as adding something like "X NPC is Assassinated" in my hidden version of the calendar. Then, when I get near that day in prep I just have to keep it in mind.
Ultimately I like it - even if it is a bit more work to track. What about you? Do you do it? How closely do you monitor time?