Seeds handled differently as of 14w04b and ongoing

What version did you use to generate the seed the first time?

Possible duplicate of MC-55596

This is the Skyblock 2.1 seed. Unknown how the original was created, however, the fact remains that structures (the Nether Fortress) is created differently using the same seed.

Re-creating should create the world only from the seed though, right?

Re-creating the world in 1.7.9 or snapshots 14w02c/14w03b generates the nether fortress at the expected coordinates (62/66/75).

After further research, the seed being handled differently is intended. When re-creating a new world, it defaults all world options and resets the world seed to the original (before it was entered).

If you want to see the Nether Fortress at the exact spot in a re-created world, just type in the seed again.

So if a brand new world is created, the command /seed is used and a new world is created using that seed number, both worlds should be EXACT.

If a new world is created using a seed in 1.7.9 and a new world is created using that same seed in 14w21b (say), those worlds are not intended to be exact and can have differences according to how the newer versions handle the seed.