From the World of Tanks official website –

The Battle of the Bulge came to a close on January 25, 1945 and we’re going to honor that date beginning on January 23, 2012.

Starting at 3:30AM PST (11:30 UTC) on January 23, 2012 and ending at 3:00AM PST (11:00 UTC) on January 26, 2012, the following discounts and bonuses will be available.

Now, the opportunity to get a Tiger at half off is pretty tempting for me.   I’ll have to unlock it first though – close, but not quite there yet.  I figure I could pick it up after one more 3x match.