If your Verizon Galaxy S4 or even a non-Verizon Galaxy S4 Alarm clock is not going off then here is a quick tip for you to fix that problem.
Go To settings > application manager > all > clock > clear data. That should fix the issue.
Or you should consider using a third party alarm app from the Google Play store, such as this one below. https://play.google.com/store/apps/details?id=com.mobilerise.alarm.clock.wake.up Or you can always consider flashing a custom rom as I have. I don’t even use that Samsung Touchwiz crap. The moment I bought my Galaxy S4, I immediately went to my laptop and flashed a new rom. Flashing a custom rom will void warranty but you can always flash back to stock ,and there are ways to reset flash counter so in the event you were to send in your S4 for warranty replacement, the technician would not know it’s been through a custom rom. The alarm app on my S4 running Liquid smooth or Slim custom roms is so reliable that I actually use it for reminders too ,and not just to wake up for work. Visit my other posts if you are serious about flashing a custom rom. Sprint http://www.techlivewire.com/2013/08/16/top-sprint-galaxy-s4-custom–roms/ AT&T http://techlivewire.com/2013/07/20/best-custom-roms-att-galaxy-s4/ T-Mobile http://techlivewire.com/2013/07/09/best-custom-rom-for-battery-life-samsung-galaxy-s4/