I mean if time 1 sec. variable int in WorldData extends by WorldSavedData will + 1 from 0 and save in nbt.

Thread name says more than post itself.

 

Anyway:

* WorldSavedData (WSD)

* WorldTickEvent (it is also kinda possible to do it with timestamps relative to World's total time, but I personally don't like that one).

 

That's it. Increment time held in WSD that would be saved/loaded to world (event.world I guess). Remember to use event.phase (Phase), you probably want START in this case.

As to WSD itself - I guess you know how to use NBT, so there is that.

 

Additional notes: Do you also need times on clients? In that case - use EntityJoinedWorldEvent to send IMessage (SimpleNetworkWrapper) to client that will set value to server's one, then - increment on both sides. I am not sure if WorldTickEvent fires for client world, so if not - you can use ClientTickEvent and Minecraft#theWorld.

Links:

http://www.minecraftforge.net/forum/index.php/topic,20135.0.html

http://greyminecraftcoder.blogspot.com.au/2015/01/thread-safety-with-network-messages.html

 

Notes: On client you can hold that value as static field anywhere really, in which case you will use ClientTickEvent to increment.

OK I understance