Well the TOS stardates were just random numbers they didn't even bother keeping in order... hence Roddenberry making an apology excuse for that one. In the TNG era, they're still ambiguous... but chronological. 1000 units represents one year pretty much without fail. 41xxx was season one... 4 for the 24th century, 1 for season 1. 42xxx for season 2 and so forth. When DS9 and Voyager came in, they just kept adding 1 each season and TNG's movies stayed consistent with that.
The smaller units... are wholly inconsistent save to say what order things happened in. Sometimes they'll go through a 100 units in a single episode with multiple log entries, sometimes it seems like it's over a month.