It never fails that at least someone misses one of those achievements that are limited due to time. Monthly achievements were a common example since they would end at reset of the last day of the month when people assumed they would go the entire month. A countdown has since been added for daily and monthly achievements.
Since the Flame and Frost living story ended, a handful of people have come to the forums complaining that they received no notice that the other achievements would be unobtainable after 12pm server time May 12th (unless otherwise mentioned). It seems there are still people that wait until the last minute and are shocked when the deadline passes.
I suggest that you extend doing the countdowns like you did for the daily and monthly to all time limited achievements. Maybe this will help with the confusion since not everyone checks the patch notes or visits the forums to see the dates.
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