Originally posted by umop-apisdn:

In my experience, using the same seed on two different days will result in slightly different results; it would appear the world generation is only semi-deterministic.

The overall look and feel of the terrain will be mostly the same, but mob spawning locations will differ slightly, as will the location and contents of instanced dungeons... never mind the trees, rocks, and other features.

The precise location and makeup of metal deposits appears to me to fall under "other features".

I would love to see proof of any differences. I've done tests in the past and have seen absolutely no difference in anything.

Version differences will make a difference, of course, and I did not try the tests on multiple days, but I don't see why the day would make a difference. If I create a world with a given seed today, and it's different if I create it again tomorrow, then the date is obviously being added to the seed, which just makes a new seed.

Any game detail that is being generated using something other than a single seed-based pseudo-random number generator would have to be both transmitted in real time between players in multiplayer and stored in the world database. Both of which make absolutely no sense for static content.

Mob spawns, changes (terrain modifications, buildings, etc), and visited locations, of course, have to be transmitted and saved.