there are mutliple ways to describle this issue
1. crontab not running
2. crontab not running and not giving error in cron log
3. crontab not running at the correct time
all this is because crond daemon process is reading the wrong time.
in my case, I set up a crontab like below
1 * * * * /bin/bash /tmp/test.sh 1 2 * * * /bin/bash /tmp/test.sh
The first line works. The second line not running at the correct time which is 2 am.
This is because crond is using a wrong time. Might because some body reset the system time but not restart crond process
原文：http://www.cnblogs.com/kramer/p/4832790.html