Issues with 1.12.2
For some reason for version 1.12.2, the SimpleDateFormat countdown timer seems to have issues with any placeholder for Hours, I'm not exactly sure how it happens but at a specific amount of time let this occurs, so far from what I can tell if your countdown is more than 1 day then it displays 24+ hours.
The placeholder used.
The outcome
Same test on other versions (1.8.9)
Issues with 1.12.2
For some reason for version 1.12.2, the SimpleDateFormat countdown timer seems to have issues with any placeholder for Hours, I'm not exactly sure how it happens but at a specific amount of time let this occurs, so far from what I can tell if your countdown is more than 1 day then it displays 24+ hours.
The placeholder used.
The outcome
Same test on other versions (1.8.9)
