The date stamp is doable and I agree it would be a good idea at least for colonies. All you'd need is an extra word because you only need to record the turn number. I doubt anyone is gonna play 65,535 turns on SE IV.
Besides being informative for the player, this could be used in the game code. A 'new' colony would be much more susceptible to panic when bad events happen, but stability would increase as the colony aged. An 'old' colony would be a more severe morale loss to the empire if it was destroyed.
The other ideas might be 'cool' but others have already observed that they might become nightmares in memory and disk space usage, not to mention bookkeeping code in the game itself.
[This message has been edited by Baron Munchausen (edited 06 November 2001).]