Xperia s alarm stuck and won't work

[Og87]

A few weeks ago the alarm app broke when clicking the clock....I really liked this app and it was easy and worked. Now it's saying alarm Thursday 08:00 on the background in the corner... but when Thursday comes nothing happens. It also won't let me click the clock icon and change it or set any other alarms.
Xperia s phone

Regular standard clock that came with the phone... not a downloaded one

[Uliwooly]

Settings > apps > alarm/clock > clear cache/data 

[Og87]

Nope didn't work still on the home page below the clock and in the corner for the lock screen as always.

[Alexander1]

This sounds really strange. Have you tried to restart the phone by press and hold the power button and volume up at the same time until the phone vibrates 3 times? 

Do you experience the same problem if you start your phone in safe mode: 

http://talk.sonymobile.com/t5/FAQ/How-to-boot-your-phone-into-safe-mode/m-p/348008#U348008