I used organically grown wet-pack Khadraway dates from the Bautista Family Date Farm. Their dates are hands down, the moistest ooey gooey dates I've ever purchased. Because regular dates from the market is usually dried, soak dates in boiling/hot water for 15-20 minutes before using for a rich and smooth cookie dough.
Their dates are seasonally available on their website: http://7hotdates.com/index.html