因为这显然是我最喜欢的答案，我将试着编辑它，以包含更多的信息。

Despite its name, NSDate in and of itself simply marks a point in machine time, not a date. There's no correlation between the point in time specified by an NSDate and a year, month, or day. For that, you have to refer to a calendar. Any given point in time will return different date information based on what calendar you're looking at (dates are not the same in both the Gregorian and Jewish calendars, for instance), and while the Gregorian calendar is the most widely used calendar in the world - I'm assuming - we're a little biased that NSDate should always use it. NSDate, luckily, is far more bipartisan.

获取日期和时间将必须通过NSCalendar，正如你提到的，但有一个更简单的方法来做它:

NSDateComponents *components = [[NSCalendar currentCalendar] components:NSCalendarUnitDay | NSCalendarUnitMonth | NSCalendarUnitYear fromDate:[NSDate date]];

它生成一个NSDateComponents对象，其中包含来自当前系统日历的日、月和年。(注意:这不一定是当前用户指定的日历，只是默认的系统日历。)

当然，如果你使用不同的日历或日期，你可以很容易地更改它。可用日历和日历单元的列表可以在NSCalendar类引用中找到。更多关于NSDateComponents的信息可以在NSDateComponents类参考中找到。

作为参考，从NSDateComponents中访问单个组件相当简单:

NSInteger day = [components day];
NSInteger month = [components month];
NSInteger year = [components year];

You just have to be mindful: NSDateComponents won't contain valid information for any fields you ask for unless you generated them with that valid information (i.e. request NSCalendar to provide that information with NSCalendarUnits). NSDateComponents contain no reference information in and of themselves - they're just simple structures that hold numbers for you to access. If you want to also get an era, for instance, out of NSDateComponents, you'll have to feed the generator method from NSCalendar with the NSCalendarUnitEra flag.

如果你想从NSDate中获得单个的NSDateComponents，你肯定需要Itai Ferber建议的解决方案。但如果你想直接从NSDate到NSString，你可以使用NSDateFormatter。

从iOS 8.0(和OS X 10)开始，你可以使用component方法来简化获取单个日期组件，如下所示:

int year = [[NSCalendar currentCalendar] component:NSCalendarUnitYear fromDate:[NSDate date]];

应该使事情更简单，希望这是有效地实施。

试试这个……

代码片段:

 NSDateComponents *components = [[NSCalendar currentCalendar] components:NSCalendarUnitDay | NSCalendarUnitMonth | NSCalendarUnitYear fromDate:[NSDate date]];
 int year = [components year];
 int month = [components month];
 int day = [components day];

它给出了当前的年、月、日

你可以使用NSDateFormatter获取NSDate的独立组件:

NSDateFormatter *df = [[NSDateFormatter alloc] init];

[df setDateFormat:@"dd"];
myDayString = [df stringFromDate:[NSDate date]];

[df setDateFormat:@"MMM"];
myMonthString = [df stringFromDate:[NSDate date]];

[df setDateFormat:@"yy"];
myYearString = [df stringFromDate:[NSDate date]];

如果你想要得到月份的数字而不是缩写，请使用“MM”。如果你想获取整数，使用[myDayString intValue];

我写这个答案是因为这是唯一的方法，不给你可选的NSDateComponent变量和/或强制展开这些变量(也适用于Swift 3)。

斯威夫特3

let date = Date()
let cal = Calendar.current
let year = cal.component(.year, from: date)
let month = cal.component(.month, from: date)
let day = cal.component(.day, from: date)

斯威夫特2

let date = NSDate()
let cal = NSCalendar.currentCalendar()
let year = cal.component(.Year, fromDate: date)
let month = cal.component(.Month, fromDate: date)
let day = cal.component(.Day, fromDate: date)

奖金Swift 3有趣的版本

let date = Date()
let component = { (unit) in return Calendar.current().component(unit, from: date) }
let year = component(.year)
let month = component(.month)
let day = component(.day)