From Grafit (http://groups.google.com/group/quartznet/browse_thread/thread/efb2582df3a6f1b4?hl=en):

CronExpression seems to have some faulty code - it doesn't handle hour
shift properly.
In GetTimeAfter, line 1358 (or smth. near)
we have code

 min++;
 d = new DateTime(d.Year, d.Month, d.Day, d.Hour, min, d.Second,
d.Millisecond);

that raises exceptions when minute was 59 - it merely gets erratically
equal to 60.
Replaced it with

                   d = d.AddMinutes(1);
and it works, but I'm a little nervous since I may have broken some
deep ideas :)).

The error occured when I made a CronTrigger launch every 5 seconds and
excluded the current day using AnnualCalendar - when GetTimeAfter is
supplied a date like (xx : 59 : 55) it fails.