This is why I tend towards the the theory of at least one missing digit in TOS stardates. For example:
Again, I usually focus only on TOS and ignore TAS, but I feel the same that TMP could be ~11.4 years after the series, say ~ Oct. 2281 (unless the Stardate clock was reset again during the period

). This gap provides plenty of time for 9 years of further adventures (books, cartoons, comics, etc.) prior to Kirk's 2.5 years flying a desk. Time enough to throw in a least one more 5YM for the TOS Enterprise, a refit to the Phase II Enterprise (if you like this concept), plus a couple of miscellaneous years with and without Kirk, then (another) refit into the TMP Enterprise.
I'm convinced that 1000 Stardates
was supposed to represent one Earth solar year (in universe, Starfleet HQ was originally governed by United Earth
on Earth, and later, by the Federation Council also located on Earth, so, why not?). Roddenberry created the vague Stardate system and gave even vaguer instructions to writers on its use primarily to: 1. keep the exact year vague; and 2. enable the format for out-of-sequence broadcast television at the time. In the end, about 5000 Stardates were use in the three Seasons, with a jerky march from Stardate ~1300 to Stardate ~6000.
Interestingly, timekeeping within the episode was mostly normal Earth time units like seconds, minutes, hours, days, months and years. In my memory, only one episode (
The Galileo Seven) used a Stardate deadline instead of a normal time unit such as two days, but even then this deadline was in reference to an official order from Galactic High Commissioner Ferris. Otherwise, Stardates were only used for official time keeping in Starfleet recordings/records.