A team will possess a player's Bird Rights during this year's 2014 Off Season Free Agency if they acquired the player on or before:
17th November, 2012
As per the Off Season Free Agency Guide:
If you own the Bird Rights to a player you are re-signing it is your job to mention this to your Player Agent! Player Agents are not expected to know whether you own a player's Bird Rights. Ensure you include not only a mention of your Bird Rights but, if you acquired your Bird Rights player whilst D5 was running, provide evidence that you own their Bird Rights by finding the trade or signing thread in which you acquired them. You may have to trawl through the season archives.