This is something I've seen ever since Beta 6 started.  As of Beta 6, when the turn starts, there is a short display of what week and year it is.  Pretty neat, although it could probably stand to be on the screen a little while longer.  Regardless, I noticed a strange bug in regards to this displaying.

If there are colony ships with automated moves and they can get to the planet they are trying to colonize at the end of turn, the game will ask if you want to colonize FOO or not.  I almost always say "No" since I want to check out the planetary bonuses (if any) before I go ahead and colonize.  The bug is, if you choose NOT to colonize a planet, the "Week XX - 22YY" banner will show up even though the turn hasn't ended yet.  Once I go ahead and finish my turn, the "Week XX - 22YY" display will not reappear once the new turn actually starts.

So far I have only seen this early notification of the Week/Year when I have not finished colonizing at the end of a turn. but I reckon that anything that will interrupt the End of Turn/Beginning of Next Turn mechanic will cause the "Week XX" banner to appear prematurely.

The ticket I just submitted for this is #PWF-384-53057.