+ (NSDateFormatter *)dateFormatter {
    static NSDateFormatter *dateFormatter;
    static dispatch_once_t onceToken;

    dispatch_once(&onceToken, ^{
        dateFormatter = [[NSDateFormatter alloc] init];
        dateFormatter.dateFormat = @"yyyy-MM-dd'T'HH:mm:ss'.000'ZZZ";
        dateFormatter.timeZone = [NSTimeZone systemTimeZone];
    });

    return dateFormatter;
}

- (void)setOccurAtWithNSString:(NSString *)string {
    self.occurAt = [[Event dateFormatter] dateFromString:string];
}

- (NSString *)JSONObjectForOccurAt {
    return self.occurAt.description;
}