They'd like you to sample the "multitude of new adventures" from the recent 2.5 update. Of course you could always start your free trial if you've never stepped foot in the realm of Eorzea before.
The free weekend starts Friday, January 30th @ 12.00am PST and it concludes Monday, February 2nd @ 12.00am PST. To be eligible you just need to have already bought the game.
"Patch 2.5 has ushered in a multitude of new adventures in the realm of Eorzea. In the hope that would-be adventurers can experience all that FFXIV: ARR has to offer, we are pleased to announce the upcoming Free Login Weekend!" announce the.
A lengthy 'Before the Fall' video for Patch 2.5 was released by Square Enix.