GetNextFireTimeUtc() returns null while trigger takes place in the futre

I am trying to delete all the triggers that have expired because Quartz.NET crashes when it faces triggers that will never be fired. So I would like to know the next fire time of my triggers and if they do not have any, then they are expired and should be removed.But now I am seeing that even a trigger that is in the future returns a null for its next fire time:

string expression = "0 26 13 17 10 ? 2015";DateTimeOffset? nextFireTimeUtc = TriggerBuilder.Create().WithCronSchedule(expression).Build().GetNextFireTimeUtc();

As can be seen my cron expression is for 2015. But nextFireTimeUtc returns null.