I think
@calypso726 gave you her experience. I just upgraded my card in May, prorated AF just posted and I haven’t paid it yet. (ETA I haven’t received my free night yet)
Here’s the official T&C
Hilton Honors Annual Free Weekend Night Reward
During each year of your Card Membership, you will receive one Annual Free Weekend Night Reward from Hilton Honors. The Annual Free Weekend Night Reward will be issued in the form of a redeemable code and sent in an email from Hilton Honors to the email address listed on your Hilton Honors account. You will receive the reward email within 8-14 weeks after opening your Card Account and each year within 8-14 weeks after your Card Account anniversary date. This benefit is only available to the Basic Card Member on the Card Account. The Annual Free Weekend Night Reward can be redeemed for one weekend night standard accommodation, double occupancy, subject to availability at properties in the Hilton portfolio, excluding those listed at
HiltonHonors.com/weekendreward. A weekend night is defined as Friday, Saturday or Sunday night. To redeem the Annual Free Weekend Night Reward, Card Members must call 1-800-446-6677 and mention the code provided by Hilton Honors.