Problem once solved already.
After sleep time change but client still see night (no sky update), same goes for use command /time set, there is no change in sky.
Reconnecting to server helps or save-load single game.
Problem occurs only on JAR versions of client, native EXE version on Windows working fine.
Easiest way to recreate problem is to run JAR server and use JAR client.
Java version tested: 1.6 and 1.7
Os: Windows 7 64bit, Ubuntu 12.10 64bit