NSPredicate compare dates in CoreData

I have a managed object with two dates: dateOne and dateTwo and I want to retrieve the dates where dateTwo is older than dateOne.

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Right now I am using the following predicate to fetch the objects:

NSArray *objects = nil;

NSFetchRequest *request = [[NSFetchRequest alloc] init];
request.entity = [NSEntityDescription entityForName:@"Object" inManagedObjectContext:context];
request.predicate = [NSPredicate predicateWithFormat:@"dateOne > dateTwo", @""];

objects = [context executeFetchRequest:request error:nil];
[request release];

Sometimes it works, but other times the objects fetched have a dateTwo that is more recent than dateOne. Is there a better way to do something like this?

Thanks!

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Perhaps you could add a BOOL property "dateTwoIsOlder" to the entity, then just fetch objects that adhere to that?

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Why not just create a fetch request from core data and not do it programmatically?