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Foundation Framework Reference NSDate Class Reference

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NSDate

Inheritance


Import Statement


Swift

import Foundation

Objective-C

@import Foundation;

Availability


Available in iOS 2.0 and later.

NSDate objects represent a single point in time. NSDate is a class cluster; its single public superclass, NSDate, declares the programmatic interface for specific and relative time values. The objects you create using NSDate are referred to as date objects. They are immutable objects. Because of the nature of class clusters, objects returned by the NSDate class are instances not of that abstract class but of one of its private subclasses. Although a date object’s class is private, its interface is public, as declared by the abstract superclass NSDate. Generally, you instantiate a suitable date object by invoking one of the date... class methods.

NSDate is an abstract class that provides behavior for creating dates, comparing dates, representing dates, computing intervals, and similar functionality. NSDate presents a programmatic interface through which suitable date objects are requested and returned. Date objects returned from NSDate are lightweight and immutable since they represent an invariant point in time. This class is designed to provide the foundation for arbitrary calendrical representations.

The sole primitive method of NSDate, timeIntervalSinceReferenceDate, provides the basis for all the other methods in the NSDate interface. This method returns a time value relative to an absolute reference date—the first instant of 1 January 2001, GMT.

To parse strings containing dates and to generate string representations of a date, you should use an instance of NSDateFormatter using the methods dateFromString: and stringFromDate: respectively—see Date Formatters for more details.

NSDate models the change from the Julian to the Gregorian calendar in October 1582, and calendrical calculations performed in conjunction with NSCalendar take this transition into account. Note, however, that some locales adopted the Gregorian calendar at other times; for example, Great Britain didn't switch over until September 1752.

NSDate is “toll-free bridged” with its Cocoa Foundation counterpart, CFDateRef. See Toll-Free Bridging for more information on toll-free bridging.

Subclassing Notes

The major reason for subclassing NSDate is to create a class with convenience methods for working with a particular calendrical system. But you could also require a custom NSDate class for other reasons, such as to get a date and time value that provides a finer temporal granularity.

Methods to Override

If you want to subclass NSDate to obtain behavior different than that provided by the private or public subclasses, you must do these things:

If you are creating a subclass that represents a calendrical system, you must also define methods that partition past and future periods into the units of this calendar.

Because the NSDate class adopts the NSCopying and NSCoding protocols, your subclass must also implement all of the methods in these protocols.

Special Considerations

Your subclass may use a different reference date than the absolute reference date used by NSDate (the first instance of 1 January 2001, GMT). If it does, it must still use the absolute reference date in its implementations of the methods timeIntervalSinceReferenceDate and initWithTimeIntervalSinceReferenceDate:. That is, the reference date referred to in the titles of these methods is the absolute reference date. If you do not use the absolute reference date in these methods, comparisons between NSDate objects of your subclass and NSDate objects of a private subclass will not work.

  • Creates and returns a new date set to the current date and time.

    Declaration

    Objective-C

    + (instancetype)date

    Return Value

    A new date object set to the current date and time.

    Discussion

    This method uses the default initializer method for the class, init.

    The following code sample shows how to use date to get the current date:

    • NSDate *today = [NSDate date];

    Import Statement

    Objective-C

    @import Foundation;

    Availability

    Available in iOS 2.0 and later.

  • Creates and returns an NSDate object set to a given number of seconds from the current date and time.

    Declaration

    Objective-C

    + (instancetype)dateWithTimeIntervalSinceNow:(NSTimeInterval)seconds

    Parameters

    seconds

    The number of seconds from the current date and time for the new date. Use a negative value to specify a date before the current date.

    Return Value

    An NSDate object set to seconds seconds from the current date and time.

    Import Statement

    Objective-C

    @import Foundation;

    Availability

    Available in iOS 2.0 and later.

  • Creates and returns an NSDate object set to a given number of seconds from the specified date.

    Declaration

    Objective-C

    + (instancetype)dateWithTimeInterval:(NSTimeInterval)seconds sinceDate:(NSDate *)date

    Parameters

    seconds

    The number of seconds to add to date. Use a negative argument to specify a date and time before date.

    date

    The date.

    Return Value

    An NSDate object set to seconds seconds from date.

    Import Statement

    Objective-C

    @import Foundation;

    Availability

    Available in iOS 4.0 and later.

  • Creates and returns an NSDate object set to a given number of seconds from the first instant of 1 January 2001, GMT.

    Declaration

    Objective-C

    + (instancetype)dateWithTimeIntervalSinceReferenceDate:(NSTimeInterval)seconds

    Parameters

    seconds

    The number of seconds from the absolute reference date (the first instant of 1 January 2001, GMT) for the new date. Use a negative argument to specify a date and time before the reference date.

    Return Value

    An NSDate object set to seconds seconds from the absolute reference date.

    Import Statement

    Objective-C

    @import Foundation;

    Availability

    Available in iOS 2.0 and later.

  • Creates and returns an NSDate object set to the given number of seconds from the first instant of 1 January 1970, GMT.

    Declaration

    Objective-C

    + (instancetype)dateWithTimeIntervalSince1970:(NSTimeInterval)seconds

    Parameters

    seconds

    The number of seconds from the reference date, 1 January 1970, GMT, for the new date. Use a negative argument to specify a date before this date.

    Return Value

    An NSDate object set to seconds seconds from the reference date.

    Discussion

    This method is useful for creating NSDate objects from time_t values returned by BSD system functions.

    Import Statement

    Objective-C

    @import Foundation;

    Availability

    Available in iOS 2.0 and later.

  • init() - init Designated Initializer

    Returns an NSDate object initialized to the current date and time.

    Declaration

    Swift

    init()

    Objective-C

    - (instancetype)init

    Return Value

    An NSDate object initialized to the current date and time.

    Discussion

    This method is a designated initializer for NSDate.

    Import Statement

    Objective-C

    @import Foundation;

    Swift

    import Foundation

    Availability

    Available in iOS 2.0 and later.

  • Returns an NSDate object initialized relative to the current date and time by a given number of seconds.

    Declaration

    Swift

    convenience init(timeIntervalSinceNow seconds: NSTimeInterval)

    Objective-C

    - (instancetype)initWithTimeIntervalSinceNow:(NSTimeInterval)seconds

    Parameters

    seconds

    The number of seconds from relative to the current date and time to which the receiver should be initialized. A negative value means the returned object will represent a date in the past.

    Return Value

    An NSDate object initialized relative to the current date and time by seconds seconds.

    Import Statement

    Objective-C

    @import Foundation;

    Swift

    import Foundation

    Availability

    Available in iOS 2.0 and later.

  • Returns an NSDate object initialized relative to another given date by a given number of seconds.

    Declaration

    Swift

    convenience init(timeInterval seconds: NSTimeInterval, sinceDate refDate: NSDate)

    Objective-C

    - (instancetype)initWithTimeInterval:(NSTimeInterval)seconds sinceDate:(NSDate *)refDate

    Parameters

    seconds

    The number of seconds to add to refDate. A negative value means the receiver will be earlier than refDate.

    refDate

    The reference date.

    Return Value

    An NSDate object initialized relative to refDate by seconds seconds.

    Import Statement

    Objective-C

    @import Foundation;

    Swift

    import Foundation

    Availability

    Available in iOS 2.0 and later.

  • Returns an NSDate object initialized relative the first instant of 1 January 2001, GMT by a given number of seconds.

    Declaration

    Swift

    init(timeIntervalSinceReferenceDate seconds: NSTimeInterval)

    Objective-C

    - (instancetype)initWithTimeIntervalSinceReferenceDate:(NSTimeInterval)seconds

    Parameters

    seconds

    The number of seconds to add to the reference date (the first instant of 1 January 2001, GMT). A negative value means the receiver will be earlier than the reference date.

    Return Value

    An NSDate object initialized relative to the absolute reference date by seconds seconds.

    Discussion

    This method is a designated initializer for the NSDate class and is declared primarily for the use of subclasses of NSDate. When you subclass NSDate to create a concrete date class, you must override this method.

    Import Statement

    Objective-C

    @import Foundation;

    Swift

    import Foundation

    Availability

    Available in iOS 2.0 and later.

  • Returns an NSDate object set to the given number of seconds from the first instant of 1 January 1970, GMT.

    Declaration

    Swift

    convenience init(timeIntervalSince1970 seconds: NSTimeInterval)

    Objective-C

    - (instancetype)initWithTimeIntervalSince1970:(NSTimeInterval)seconds

    Parameters

    seconds

    The number of seconds from the reference date, 1 January 1970, GMT, for the new date. Use a negative argument to specify a date before this date.

    Return Value

    An NSDate object set to seconds seconds from the reference date.

    Discussion

    This method is useful for creating NSDate objects from time_t values returned by BSD system functions.

    Import Statement

    Objective-C

    @import Foundation;

    Swift

    import Foundation

    Availability

    Available in iOS 4.0 and later.

  • Creates and returns an NSDate object representing a date in the distant future.

    Declaration

    Swift

    class func distantFuture() -> AnyObject

    Objective-C

    + (id)distantFuture

    Return Value

    An NSDate object representing a date in the distant future (in terms of centuries).

    Discussion

    You can pass this value when an NSDate object is required to have the date argument essentially ignored. For example, the NSWindow method nextEventMatchingMask:untilDate:inMode:dequeue: returns nil if an event specified in the event mask does not happen before the specified date. You can use the object returned by distantFuture as the date argument to wait indefinitely for the event to occur.

    • myEvent = [myWindow nextEventMatchingMask:myEventMask
    • untilDate:[NSDate distantFuture]
    • inMode:NSDefaultRunLoopMode
    • dequeue:YES];

    Import Statement

    Objective-C

    @import Foundation;

    Swift

    import Foundation

    Availability

    Available in iOS 2.0 and later.

    See Also

    + distantPast

  • Creates and returns an NSDate object representing a date in the distant past.

    Declaration

    Swift

    class func distantPast() -> AnyObject

    Objective-C

    + (id)distantPast

    Return Value

    An NSDate object representing a date in the distant past (in terms of centuries).

    Discussion

    You can use this object as a control date, a guaranteed temporal boundary.

    Import Statement

    Objective-C

    @import Foundation;

    Swift

    import Foundation

    Availability

    Available in iOS 2.0 and later.

    See Also

    + distantFuture

  • Returns a Boolean value that indicates whether a given object is an NSDate object and exactly equal the receiver.

    Declaration

    Swift

    func isEqualToDate(_ anotherDate: NSDate) -> Bool

    Objective-C

    - (BOOL)isEqualToDate:(NSDate *)anotherDate

    Parameters

    anotherDate

    The date to compare with the receiver.

    Return Value

    Yes if the anotherDate is an NSDate object and is exactly equal to the receiver, otherwise NOfalse.

    Discussion

    This method detects sub-second differences between dates. If you want to compare dates with a less fine granularity, use timeIntervalSinceDate: to compare the two dates.

    Import Statement

    Objective-C

    @import Foundation;

    Swift

    import Foundation

    Availability

    Available in iOS 2.0 and later.

  • Returns the earlier of the receiver and another given date.

    Declaration

    Swift

    func earlierDate(_ anotherDate: NSDate) -> NSDate

    Objective-C

    - (NSDate *)earlierDate:(NSDate *)anotherDate

    Parameters

    anotherDate

    The date with which to compare the receiver.

    Return Value

    The earlier of the receiver and anotherDate, determined using timeIntervalSinceDate:. If the receiver and anotherDate represent the same date, returns the receiver.

    Import Statement

    Objective-C

    @import Foundation;

    Swift

    import Foundation

    Availability

    Available in iOS 2.0 and later.

    See Also

    – compare:
    isEqual: (NSObject protocol)
    – laterDate:

  • Returns the later of the receiver and another given date.

    Declaration

    Swift

    func laterDate(_ anotherDate: NSDate) -> NSDate

    Objective-C

    - (NSDate *)laterDate:(NSDate *)anotherDate

    Parameters

    anotherDate

    The date with which to compare the receiver.

    Return Value

    The later of the receiver and anotherDate, determined using timeIntervalSinceDate:. If the receiver and anotherDate represent the same date, returns the receiver.

    Import Statement

    Objective-C

    @import Foundation;

    Swift

    import Foundation

    Availability

    Available in iOS 2.0 and later.

    See Also

    – compare:
    – earlierDate:
    isEqual: (NSObject protocol)

  • Returns an NSComparisonResult value that indicates the temporal ordering of the receiver and another given date.

    Declaration

    Swift

    func compare(_ anotherDate: NSDate) -> NSComparisonResult

    Objective-C

    - (NSComparisonResult)compare:(NSDate *)anotherDate

    Parameters

    anotherDate

    The date with which to compare the receiver.

    This value must not be nil. If the value is nil, the behavior is undefined and may change in future versions of OS X.

    Return Value

    If:

    • The receiver and anotherDate are exactly equal to each other, NSOrderedSame

    • The receiver is later in time than anotherDate, NSOrderedDescending

    • The receiver is earlier in time than anotherDate, NSOrderedAscending.

    Discussion

    This method detects sub-second differences between dates. If you want to compare dates with a less fine granularity, use timeIntervalSinceDate: to compare the two dates.

    Import Statement

    Objective-C

    @import Foundation;

    Swift

    import Foundation

    Availability

    Available in iOS 2.0 and later.

    See Also

    – earlierDate:
    isEqual: (NSObject protocol)
    – laterDate:

  • Returns a new NSDate object that is set to a given number of seconds relative to the receiver.

    Declaration

    Swift

    func dateByAddingTimeInterval(_ seconds: NSTimeInterval) -> Self

    Objective-C

    - (instancetype)dateByAddingTimeInterval:(NSTimeInterval)seconds

    Parameters

    seconds

    The number of seconds to add to the receiver. Use a negative value for seconds to have the returned object specify a date before the receiver.

    Return Value

    A new NSDate object that is set to seconds seconds relative to the receiver. The date returned might have a representation different from the receiver’s.

    Import Statement

    Objective-C

    @import Foundation;

    Swift

    import Foundation

    Availability

    Available in iOS 2.0 and later.

  • Returns a new NSDate object that is set to a given number of seconds relative to the receiver.

    Deprecation Statement

    This method has been replaced by dateByAddingTimeInterval:.

    Declaration

    Objective-C

    - (id)addTimeInterval:(NSTimeInterval)seconds

    Parameters

    seconds

    The number of seconds to add to the receiver. Use a negative value for seconds to have the returned object specify a date before the receiver.

    Return Value

    A new NSDate object that is set to seconds seconds relative to the receiver. The date returned might have a representation different from the receiver’s.

    Import Statement

    Objective-C

    @import Foundation;

    Availability

    Available in iOS 2.0 and later.

    Deprecated in iOS 4.0.

  • A string representation of the date object. (read-only)

    Declaration

    Swift

    var description: String { get }

    Objective-C

    @property(readonly, copy) NSString *description

    Discussion

    The representation is useful for debugging only.

    There are a number of options to acquire a formatted string for a date including: date formatters (see NSDateFormatter and Data Formatting Guide), and the NSDate methods descriptionWithLocale:, dateWithCalendarFormat:timeZone:, and descriptionWithCalendarFormat:timeZone:locale:

    Import Statement

    Objective-C

    @import Foundation;

    Swift

    import Foundation

    Availability

    Available in iOS 2.0 and later.

  • Returns a string representation of the receiver using the given locale.

    Declaration

    Swift

    func descriptionWithLocale(_ locale: AnyObject?) -> String?

    Objective-C

    - (NSString *)descriptionWithLocale:(id)locale

    Parameters

    locale

    An NSLocale object.

    If you pass nil, NSDate formats the date in the same way as the description property.

    On OS X v10.4 and earlier, this parameter was an NSDictionary object. If you pass in an NSDictionary object on OS X v10.5, NSDate uses the default user locale—the same as if you passed in [NSLocale currentLocale].

    Return Value

    A string representation of the receiver, using the given locale, or if the locale argument is nil, in the international format YYYY-MM-DD HH:MM:SS ±HHMM, where ±HHMM represents the time zone offset in hours and minutes from GMT (for example, “2001-03-24 10:45:32 +0600”)

    Special Considerations

    On OS X v10.4 and earlier, localeDictionary is an NSDictionary object containing locale data. To use the user's preferences, you can use [[NSUserDefaults standardUserDefaults] dictionaryRepresentation].

    Import Statement

    Objective-C

    @import Foundation;

    Swift

    import Foundation

    Availability

    Available in iOS 4.0 and later.

  • NSDate provides a constant that specifies the number of seconds from 1 January 1970 to the reference date, 1 January 2001.

    Declaration

    Swift

    var NSTimeIntervalSince1970: Double { get }

    Objective-C

    #define NSTimeIntervalSince1970 978307200.0

    Constants

    • NSTimeIntervalSince1970

      NSTimeIntervalSince1970

      The number of seconds from 1 January 1970 to the reference date, 1 January 2001.

      Available in iOS 2.0 and later.

    Discussion

    1 January 1970 is the epoch (or starting point) for Unix time.

  • Posted whenever the system clock is changed. This can be initiated by a call to settimeofday() or the user changing values in the Date and Time Preference panel. The notification object is null. This notification does not contain a userInfo dictionary.

    Import Statement

    Objective-C

    @import Foundation;

    Swift

    import Foundation

    Availability

    Available in iOS 4.0 and later.