For those who still suffering from this issue:
1.Go to Setting > Date and Time > Date format > Regional
OR
2.The alarm clock's glitch happened when you have your sound volume totally off , so simply turn on your sound volume and its all good.
Neither of these work for me...I've had to factory reset the phone more than once (as per att tech support) and nothing works. this is one of many issues with my s6 edge
