If you consider the five year mission and the movies, what is the time from which you could write stories about the ToS crew without functionaly breaking known canon?
For example;
How much time is between TMP and the end of TOS timeline wise?
How much time has the crew been together before the first episode of TOS?
For example;
How much time is between TMP and the end of TOS timeline wise?
How much time has the crew been together before the first episode of TOS?