Over the past few days we were facing a issue with the future posts feature in WordPress, while the future posts correctly showed a timer to the scheduled time, once it reached the scheduled it started in reverse direction and the timer went from 1 minute to 2 minutes and so on.
To top that, we also had a issue where few of our post dated future posts published ahead of time. This was particularly frustrating and we checked several things such as server time, WordPress time stamp and other possible places where we could find out the problem.
After trying for a couple of days, we finally figured narrowed the issue to one of the changes we made to WordPress Timezone to adjust the clock for Daylight savings time. It turns out that WordPress is not pretty good at handling Daylight savings time and this caused a problem with the future posts. We went back and corrected the timing back to not include the Daylight savings adjustment and our future posts started working fine again.
So if you have made changes to your Timezone and are seeing issues with future posts, just revert the settings to normal time without DST and your future posts should work fine.