I have a cron \"time definition\"
1 * * * * (every hour at xx:01) 2 5 * * * (every day at 05:02) 0 4 3 * * (every third day of the month at 04:00) * 2 * * 5
Created javascript API for calculating next run time based on @dlamblin idea. Supports seconds and years. Have not managed to test it fully yet so expect bugs but let me know if find any.
Repository link: https://bitbucket.org/nevity/cronner