When does the Temporal Prime Directive get codified?

Question

We know that in "Assignment: Earth", in 2268, the time travel method discovered in 2267 ("Tomorrow is Yesterday") is considered a standard research tool. In 2286, it's considered a reasonable technique to capture animals from 1986 Earth (ST IV: The Voyage Home): Kirk is charged with insubordination, not violating the Temporal Prime Directive.

In the Voyager episode "Timeless", we see that in a potential version of circa 2390 Chakotay and Kim are fleeing from charges including "conspiracy to violate the Temporal Prime Directive".

Do we know when, in this century-wide window, the Temporal Prime Directive first gets codified? Note that this is different from "when is the Temporal Prime Directive first expressed" because 29th century enforcement officers go back to various points in history and describe the directive to people, including possibly at times before the directive was codified.

Answer 1

In-Universe the Temporal Prime Directive seems to have been codified (as standard Starfleet Policy) some time between 2368 and 2371.

In 2368 in TNG: A Matter of Time Picard moots the possibility that people from the future (with ready access to easy and convenient time travel) may have some sort of Prime Directive-like rule that prevents them from changing the past. This would strongly suggest that Picard himself isn't held to the same strictures.

PICARD: Of course, you know of the Prime Directive, which tells us that we have no right to interfere with the natural evolution of alien worlds. Now I have sworn to uphold it, but nevertheless I have disregarded that directive on more than one occasion because I thought it was the right thing to do. Now, if you are holding on to some temporal equivalent of that directive, then isn't it possible that you have an occasion here to make an exception, to help me to choose, because it's the right thing to do?

_{^{TNG: A Matter of Time}}

By 2371 in VOY: Shattered Janeway explictly mentions that the Temporal Prime Directive is now standard Starfleet policy

CHAKOTAY: It's a long story.

JANEWAY: Maybe you should keep it to yourself. The Temporal Prime Directive. The less I know about the future, the better.

_{^{Voy: Shattered}}

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Prior to this point Starfleet captains seem to have been given broad latitude to determine whether their actions were pre-determined or liable to disrupt the timelime, hence why Edith Keeler had to die. Starfleet also seems happy to allow the rule against time travel to be breached when the survival of the Federation is a stake.