let date: Date = Date()

NSDate *date = [NSDate date];

let calendar: Calendar = Calendar(identifier: .gregorian)
print("Year:", calendar.component(.year, from: date))
print("Month:", calendar.component(.month, from: date))
print("Day:", calendar.component(.day, from: date))

NSCalendar *calendar = [NSCalendar calendarWithIdentifier:NSCalendarIdentifierGregorian];
NSLog(@"Year: %ld", [calendar component:NSCalendarUnitYear fromDate:date]);
NSLog(@"Month: %ld", [calendar component:NSCalendarUnitMonth fromDate:date]);
NSLog(@"Day: %ld", [calendar component:NSCalendarUnitDay fromDate:date]);

let componentSet: Set<Calendar.Component> = Set(arrayLiteral: .year, .month, .day)
let components: DateComponents = calendar.dateComponents(componentSet, from: date)
print("Year:", components.year!)
print("Month:", components.month!)
print("Day:", components.day!)

NSCalendarUnit calenderUnit = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay;
NSDateComponents *components = [calendar components:calenderUnit fromDate:date];
NSLog(@"Year: %ld", components.year);
NSLog(@"Month: %ld", components.month);
NSLog(@"Day: %ld", components.day);

let formatter: DateFormatter = DateFormatter()
print("Date formatter identifier:", formatter.calendar.identifier) // gregorian by default
formatter.dateFormat = "y"
print("Year:", formatter.string(from: date))
formatter.dateFormat = "M"
print("Month:", formatter.string(from: date))
formatter.dateFormat = "d"
print("Day:", formatter.string(from: date))

NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
NSLog(@"Date formatter calendar: %@", formatter.calendar.calendarIdentifier); // gregorian by default
formatter.dateFormat = @"y";
NSLog(@"Year: %@", [formatter stringFromDate:date]);
formatter.dateFormat = @"M";
NSLog(@"Month: %@", [formatter stringFromDate:date]);
formatter.dateFormat = @"d";
NSLog(@"Day: %@", [formatter stringFromDate:date]);

let calendar: Calendar = Calendar(identifier: .chinese)

NSCalendar *calendar = [NSCalendar calendarWithIdentifier:NSCalendarIdentifierChinese];

let formatter: DateFormatter = DateFormatter()
formatter.calendar = Calendar(identifier: .chinese)

NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
formatter.calendar = [NSCalendar calendarWithIdentifier:NSCalendarIdentifierChinese];

ChineseCalendar 的类方法
static func zodiac(withYear year: Int) -> String {
 let zodiacIndex: Int = (year - 1) % Zodiacs.count
 return Zodiacs[zodiacIndex]
}
 
static func zodiac(withDate date: Date) -> String {
 let calendar: Calendar = Calendar(identifier: .chinese)
 return zodiac(withYear: calendar.component(.year, from: date))
}

print("Chinese zodiac string:", ChineseCalendar.zodiac(withDate: date))

private let HeavenlyStems: [String] = ["甲", "乙", "丙", "丁", "戊", "己", "庚", "辛", "壬", "癸"]
private let EarthlyBranches: [String] = ["子", "丑", "寅", "卯", "辰", "巳", "午", "未", "申", "酉", "戌", "亥"]

static func era(withYear year: Int) -> String {
 let heavenlyStemIndex: Int = (year - 1) % HeavenlyStems.count
 let heavenlyStem: String = HeavenlyStems[heavenlyStemIndex]
 let earthlyBrancheIndex: Int = (year - 1) % EarthlyBranches.count
 let earthlyBranche: String = EarthlyBranches[earthlyBrancheIndex]
 return heavenlyStem + earthlyBranche
}
 
static func era(withDate date: Date) -> String {
 let calendar: Calendar = Calendar(identifier: .chinese)
 return era(withYear: calendar.component(.year, from: date))
}

print("Chinese era string:", ChineseCalendar.era(withDate: date))