Originally Posted by
rj123456
Contrary to what I have read in some blogs and on here, Chase has informed me that:
I had a transaction on 12/31/17 that posted on 01/01/18. I was slow to use up the 2017 credits and they used up my 2018 credits

It's clearly stated by Chase--even with an example--in the offer details for the card. Where did you read otherwise?
Annual credit will be issued for the calendar year in which the transaction posts to your account. For example, if you pay baggage fees at the end of 2015, and the airline does not post the transaction until 2016, the cost of the baggage fees will be allocated towards your 2016 calendar year maximum of $300.