NCrontab library needs GetPreviousOccurence method on CrontabSchedule

Job ID: 35844752

Budget: $10 – $30 USD

Need to implement the feature asked for in atifaziz/NCrontab#64 (https://github.com/atifaziz/NCrontab/issues/64).
This would be a new method on the same class that GetNextOccurrence method (https://github.com/atifaziz/NCrontab/blob/master/NCrontab/CrontabSchedule.cs#L192) is on. It would preform the same function but in reverse from the DateTime provided.
It would need unit tests like the ones at https://github.com/atifaziz/NCrontab/blob/master/NCrontab.Tests/CrontabScheduleTests.cs#L417 and https://github.com/atifaziz/NCrontab/blob/master/NCrontab.Tests/CrontabScheduleTests.cs#L404
Related categories: .NET C# Programming Mathematics