日期转换为星期

NSArray *weekdays = [NSArray arrayWithObjects: [NSNull null], @"日", @"一", @"二", @"三", @"四", @"五", @"六", nil];

NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];

NSTimeZone *timeZone = [[NSTimeZone alloc] initWithName:@"Asia/Shanghai"];

[calendar setTimeZone: timeZone];
NSCalendarUnit calendarUnit = NSCalendarUnitWeekday;

NSDateComponents *theComponents = [calendar components:calendarUnit fromDate:date];

if(theComponents.weekday >= weekdays.count) {
return @”“;
}
return [weekdays objectAtIndex:theComponents.weekday];