There was a bug which appeared because of the clock change, and those players took advantage of it.
All researches above 12h that were in queue, if you changed them
http://prntscr.com/6mec1b in a few minutes it would cut down the research time by 1 hour
http://prntscr.com/6mefax. But the time under 12 hours could not be shortened so i guess they used diamonds for the last 12 hours for instant research.
I'm sorry but bugs like this appear when there is a change in the server time.