NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *components = [calendar components:(NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay) fromDate:myNSDateInstance];
NSInteger year = [components year];
// NSInteger month = [components month];
NSString *yearStr = [NSString stringWithFormat:@"%ld", year];

网络上有很多NSDate的助手，我倾向于使用:

https://github.com/billymeltdown/nsdate-helper/

自述摘录如下:

  NSString *displayString = [NSDate stringForDisplayFromDate:date];

这将产生以下类型的输出:

‘3:42 AM’ – if the date is after midnight today
‘Tuesday’ – if the date is within the last seven days
‘Mar 1’ – if the date is within the current calendar year
‘Mar 1, 2008’ – else ;-)

如果你没有NSDate -descriptionWithCalendarFormat:timeZone:locale: available(我不相信iPhone/Cocoa Touch包括这个)，你可能需要使用strftime和一些c风格的字符串。您可以使用NSDate -timeIntervalSince1970从NSDate中获取UNIX时间戳。

swift格式:

func dateFormatterWithCalendar(calndarIdentifier: Calendar.Identifier, dateFormat: String) -> DateFormatter {

    let formatter = DateFormatter()
    formatter.calendar = Calendar(identifier: calndarIdentifier)
    formatter.dateFormat = dateFormat

    return formatter
}


//Usage
let date = Date()
let fotmatter = dateFormatterWithCalendar(calndarIdentifier: .gregorian, dateFormat: "yyyy")
let dateString = fotmatter.string(from: date)
print(dateString) //2018

NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *components = [calendar components:(NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay) fromDate:myNSDateInstance];
NSInteger year = [components year];
// NSInteger month = [components month];
NSString *yearStr = [NSString stringWithFormat:@"%ld", year];

如何……

NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"yyyy"];

//Optionally for time zone conversions
[formatter setTimeZone:[NSTimeZone timeZoneWithName:@"..."]];

NSString *stringFromDate = [formatter stringFromDate:myNSDateInstance];

//unless ARC is active
[formatter release];

Swift 4.2:

func stringFromDate(_ date: Date) -> String {
    let formatter = DateFormatter()
    formatter.dateFormat = "dd MMM yyyy HH:mm" //yyyy
    return formatter.string(from: date)
}