+ (NSString*)weekdayStringFromDate:(NSDate*)inputDate {    NSArray *weekdays = [NSArray arrayWithObjects: [NSNull null], @"Sunday", @"周一", @"周二", @"周三", @"周四", @"周五", @"周六", nil];    NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];    NSTimeZone *timeZone = [[NSTimeZone alloc] initWithName:@"Asia/Shanghai"];    [calendar setTimeZone: timeZone];    NSCalendarUnit calendarUnit = NSWeekdayCalendarUnit;    NSDateComponents *theComponents = [calendar components:calendarUnit fromDate:inputDate];return [weekdays objectAtIndex:theComponents.weekday];}