feature request: GetPriorOccurrence

Would you please consider returning the return the DateTime when a task would have been due going back in time.

I am currently using the real hack

_expression.GetOccurrences(scheduled.AddDays(-60), scheduled, _timeZoneInfo, false, false).Last();

[RZeni]

This was the workaround that worked best for me. In my case a default of 1 month ago was sufficient, a more general use case probably wants a null default.

`

public DateTime GetPreviousOccurence(string cronString)
{
    var expression = CronExpression.Parse(cronString);
    var nextCron = expression.GetNextOccurrence(DateTime.UtcNow);

    if (nextCron == null) return DateTime.Now.AddMonths(-1);
    var upperBound = expression.GetNextOccurrence(nextCron.Value);

    if (upperBound == null) return DateTime.Now.AddMonths(-1);
    var difference = upperBound.Value.Subtract(nextCron.Value);

    return DateTime.Now.Subtract(difference);
}

`

[odinserj]

Please describe the idea behind this feature – we need to understand when it’s required, because usually we are iterating forward.