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I'm trying to find the oldest date in a particular attribute in Core Data. I've found an example in the Core Data Programming Guide that purports to do exactly that, but keep getting an unrecognized selected error when I run it. My code (with only minimal changes from the Apple Example): NSFetchRequest *request = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Session" inManagedObjectContext: ctx]; [request setEntity:entity]; // Specify that the request should return dictionaries. [request setResultType:NSDictionaryResultType]; // Create an expression for the key path. NSExpression *keyPathExpression = [NSExpression expressionForKeyPath:@"startedAt"]; // Create an expression to represent the minimum value at the key path 'creationDate' NSExpression *minExpression = [NSExpression expressionForFunction:@"min:" arguments:[NSArray arrayWithObject:keyPathExpression]]; // Create an expression description using the minExpression and returning a date. NSExpressionDescription *expressionDescription = [[NSExpressionDescription alloc] init]; // The name is the key that will be used in the dictionary for the return value. [expressionDescription setName:@"minDate"]; [expressionDescription setExpression:minExpression]; [expressionDescription setExpressionResultType:NSDateAttributeType]; // Set the request's properties to fetch just the property represented by the expressions. [request setPropertiesToFetch:[NSArray arrayWithObject:expressionDescription]]; // Execute the fetch. NSError *error; NSArray *objects = [ctx executeFetchRequest:request error:&error]; And the error: -[NSCalendarDate count]: unrecognized selector sent to instance ... Which is strange given that 1) NSCal

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