I just checked on the FC website where they show the preview of benefits for new members and this is what it said about Diamond Status:
Please allow up to six weeks for upgrade. Upon being upgraded, your status is valid through March 31, 2016.
Must be 21+ to redeem this benefit.
* Where available. Fees or other restrictions may apply. Please see Total Rewards Center for complete details.
** Cash/Credit purchases only. Some items may be excluded from this discount. Please see Total Rewards Center or retail outlet for any restrictions.