NSDate Comparison using Swift

Question

I am working on an app the requires checking the due date for homework. I want to know if a due date is within the next week, and if it is then perform an action.
Most of the documentation I could find is in Objective-C and I can't figure out how to do it in Swift. Thanks for the help!!

swift does not have a date class you use the Objective C NSDate class - so you have found the correct documentation — mmmmmm, Commented Oct 5, 2014 at 0:52
Possible duplicate of Comparing NSDates without time component. There are lots of very good answers. — jww, Commented Oct 5, 2014 at 0:56
Swift 3 does have a Date class. It is bridged to NSDate, but it is called Date. — BallpointBen, Commented Mar 9, 2017 at 22:01

John Estropia · Accepted Answer · 2015-01-23 12:31:55Z

210

If you want to support ==, <, >, <=, or >= for NSDates, you just have to declare this somewhere:

public func ==(lhs: NSDate, rhs: NSDate) -> Bool {
    return lhs === rhs || lhs.compare(rhs) == .OrderedSame
}

public func <(lhs: NSDate, rhs: NSDate) -> Bool {
    return lhs.compare(rhs) == .OrderedAscending
}

extension NSDate: Comparable { }

answered Jan 23, 2015 at 12:31

John Estropia

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2

@Isuru Comparable is a descendant of the Equatable protocol so you shouldn't need to declare conformance to both.
– John Estropia
Commented Jul 23, 2015 at 2:00
2

Just curious why it isn't built in by default?!
– Dmitry
Commented Dec 18, 2015 at 17:34
3

@dVaffection In Objective-C (where NSDate and friends are declared), if you compare using ==, <, >, etc., you'll be getting a result of the comparison of their address in memory, not the comparison of their actual value. In Swift, they are still treated as references so I think the choice was to either (1) keep by-pointer-comparisons as they are in ObjC, or (2) eliminate confusion by not providing an implementation for comparisons.
– John Estropia
Commented Dec 22, 2015 at 5:01
2

An added benefit of this approach is that Array.maxElement(), etc is then automatically available of arrays of NSDates.
– pr1001
Commented Jan 4, 2016 at 21:02
1

@MarcioCruz That's just a Swift requirement that all operator implementations should be at the global scope. See the discussion here: stackoverflow.com/questions/35246003/…
– John Estropia
Commented Feb 24, 2016 at 4:06

| Show 8 more comments

iamburak · Accepted Answer · 2019-04-23 11:35:46Z

I like using extensions to make code more readable. Here are a few NSDate extensions that can help clean your code up and make it easy to understand. I put this in a sharedCode.swift file:

extension NSDate {

    func isGreaterThanDate(dateToCompare: NSDate) -> Bool {
        //Declare Variables
        var isGreater = false

        //Compare Values
        if self.compare(dateToCompare as Date) == ComparisonResult.orderedDescending {
            isGreater = true
        }

        //Return Result
        return isGreater
    }

    func isLessThanDate(dateToCompare: NSDate) -> Bool {
        //Declare Variables
        var isLess = false

        //Compare Values
        if self.compare(dateToCompare as Date) == ComparisonResult.orderedAscending {
            isLess = true
        }

        //Return Result
        return isLess
    }

    func equalToDate(dateToCompare: NSDate) -> Bool {
        //Declare Variables
        var isEqualTo = false

        //Compare Values
        if self.compare(dateToCompare as Date) == ComparisonResult.orderedSame {
            isEqualTo = true
        }

        //Return Result
        return isEqualTo
    }

    func addDays(daysToAdd: Int) -> NSDate {
        let secondsInDays: TimeInterval = Double(daysToAdd) * 60 * 60 * 24
        let dateWithDaysAdded: NSDate = self.addingTimeInterval(secondsInDays)

        //Return Result
        return dateWithDaysAdded
    }

    func addHours(hoursToAdd: Int) -> NSDate {
        let secondsInHours: TimeInterval = Double(hoursToAdd) * 60 * 60
        let dateWithHoursAdded: NSDate = self.addingTimeInterval(secondsInHours)

        //Return Result
        return dateWithHoursAdded
    }
}

Now if you can do something like this:

//Get Current Date/Time
var currentDateTime = NSDate()

//Get Reminder Date (which is Due date minus 7 days lets say)
var reminderDate = dueDate.addDays(-7)

//Check if reminderDate is Greater than Right now
if(reminderDate.isGreaterThanDate(currentDateTime)) {
    //Do Something...
}

You should simplify your code. return self.compare(dateToCompare) == NSComparisonResult.OrderedDescending — Olav Gausaker, Commented Apr 9, 2015 at 14:54
isEqualToDate is provided by Apple as well. It's declaration conflicts with the one defined by Apple. — Shamas S, Commented Jun 22, 2015 at 10:09
This answer is terrible and should never be the accepted one. Don't ever add time intervals to dates that are created by you. That's precisely why NSDateComponents exist. There are a lot of edge cases that are not being handle properly and it makes no sense not to add conformance to Comparable to NSDate. I'd recommend using John's solution. — fpg1503, Commented Feb 17, 2016 at 21:50
A better solution is to make NSDate Equatable, Comparable, then you could simply do date1 < date2 — aryaxt, Commented Mar 11, 2016 at 16:04

Undo · Accepted Answer · 2016-06-05 23:23:16Z

This is how you compare two NSDates in Swift, I just tested it in Xcode's playground:

if date1.compare(date2) == NSComparisonResult.OrderedDescending
{
    NSLog("date1 after date2");
} else if date1.compare(date2) == NSComparisonResult.OrderedAscending
{
    NSLog("date1 before date2");
} else
{
    NSLog("dates are equal");
}

So to check if a date dueDate is within a week from now:

let dueDate=...

let calendar = NSCalendar.currentCalendar()
let comps = NSDateComponents()
comps.day = 7
let date2 = calendar.dateByAddingComponents(comps, toDate: NSDate(), options: NSCalendarOptions.allZeros)

if dueDate.compare(date2!) == NSComparisonResult.OrderedDescending
{
    NSLog("not due within a week");
} else if dueDate.compare(date2!) == NSComparisonResult.OrderedAscending
{
    NSLog("due within a week");
} else
{
    NSLog("due in exactly a week (to the second, this will rarely happen in practice)");
}

do ordered Descending means that date1 > date2?
– Henry oscannlain-miller
Commented Oct 5, 2014 at 1:01 — Henry oscannlain-miller, Commented Oct 5, 2014 at 1:01
Yes, @Henryoscannlain-miller.
– Undo ♦
Commented Oct 5, 2014 at 1:02 — Undo, Commented Oct 5, 2014 at 1:02

ReDetection · Accepted Answer · 2015-09-25 05:43:49Z

47

I always did it in one line:

let greater = date1.timeIntervalSince1970 < date2.timeIntervalSince1970

Still readable in the if block

answered Sep 25, 2015 at 5:43

ReDetection

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AechoLiu · Accepted Answer · 2016-11-17 02:20:28Z

In Swift3, the Date struct in the Foundation now implements the Comparable protocol. So, the previous Swift2 NSDate approaches are superceded by Swift3 Date.

/**
 `Date` represents a single point in time.

 A `Date` is independent of a particular calendar or time zone. To represent a `Date` to a user, you must interpret it in the context of a `Calendar`.
*/
public struct Date : ReferenceConvertible, Comparable, Equatable {

    // .... more         

    /**
        Returns the interval between the receiver and another given date.

        - Parameter another: The date with which to compare the receiver.

        - Returns: The interval between the receiver and the `another` parameter. If the receiver is earlier than `anotherDate`, the return value is negative. If `anotherDate` is `nil`, the results are undefined.

        - SeeAlso: `timeIntervalSince1970`
        - SeeAlso: `timeIntervalSinceNow`
        - SeeAlso: `timeIntervalSinceReferenceDate`
        */
    public func timeIntervalSince(_ date: Date) -> TimeInterval

   // .... more 

    /// Returns true if the two `Date` values represent the same point in time.
    public static func ==(lhs: Date, rhs: Date) -> Bool

    /// Returns true if the left hand `Date` is earlier in time than the right hand `Date`.
    public static func <(lhs: Date, rhs: Date) -> Bool

    /// Returns true if the left hand `Date` is later in time than the right hand `Date`.
    public static func >(lhs: Date, rhs: Date) -> Bool

    /// Returns a `Date` with a specified amount of time added to it.
    public static func +(lhs: Date, rhs: TimeInterval) -> Date

    /// Returns a `Date` with a specified amount of time subtracted from it.
    public static func -(lhs: Date, rhs: TimeInterval) -> Date

  // .... more
}

Note ...

In Swift3, Date is struct, it means that it is value type. NSDate is class, it is reference type.

// Swift3
let a = Date()
let b = a //< `b` will copy `a`. 

// So, the addresses between `a` and `b` are different.
// `Date` is some kind different with `NSDate`.

Yurii Voievodin · Accepted Answer · 2016-04-04 06:17:24Z

extension NSDate {

    // MARK: - Dates comparison

    func isGreaterThanDate(dateToCompare: NSDate) -> Bool {

        return self.compare(dateToCompare) == NSComparisonResult.OrderedDescending
    }

    func isLessThanDate(dateToCompare: NSDate) -> Bool {

        return self.compare(dateToCompare) == NSComparisonResult.OrderedAscending
    }

    func equalToDate(dateToCompare: NSDate) -> Bool {

        return self.compare(dateToCompare) == NSComparisonResult.OrderedSame
    }
}

SashaZ · Accepted Answer · 2016-10-05 08:28:03Z

6

If you want to compare dates with granularity (just same day or year etc) on swift 3.

func compareDate(date1:NSDate, date2:NSDate, toUnitGranularity: NSCalendar.Unit) -> Bool {

 let order = NSCalendar.current.compare(date1 as Date, to: date2 as Date, toGranularity: .day)
 switch order {
 case .orderedSame:
   return true
 default:
   return false
 }
}

For other calendar comparisons change .day to;

.year .month .day .hour .minute .second

answered Oct 5, 2016 at 8:28

SashaZ

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Trung Phan · Accepted Answer · 2017-03-11 15:53:10Z

Swift already implement Date comparison just use date1 > date2 and so on.

/// Returns true if the two `Date` values represent the same point in time.
public static func ==(lhs: Date, rhs: Date) -> Bool

/// Returns true if the left hand `Date` is earlier in time than the right hand `Date`.
public static func <(lhs: Date, rhs: Date) -> Bool

/// Returns true if the left hand `Date` is later in time than the right hand `Date`.
public static func >(lhs: Date, rhs: Date) -> Bool

/// Returns a `Date` with a specified amount of time added to it.
public static func +(lhs: Date, rhs: TimeInterval) -> Date

/// Returns a `Date` with a specified amount of time subtracted from it.
public static func -(lhs: Date, rhs: TimeInterval) -> Date

/// Add a `TimeInterval` to a `Date`.
///
/// - warning: This only adjusts an absolute value. If you wish to add calendrical concepts like hours, days, months then you must use a `Calendar`. That will take into account complexities like daylight saving time, months with different numbers of days, and more.
public static func +=(lhs: inout Date, rhs: TimeInterval)

/// Subtract a `TimeInterval` from a `Date`.
///
/// - warning: This only adjusts an absolute value. If you wish to add calendrical concepts like hours, days, months then you must use a `Calendar`. That will take into account complexities like daylight saving time, months with different numbers of days, and more.
public static func -=(lhs: inout Date, rhs: TimeInterval)

Suhit Patil · Accepted Answer · 2017-03-18 12:34:32Z

in Swift 3, Date is Comparable so we can directly compare dates like

let date1 = Date()
let date2 = Date()

let isGreater = date1 > date2
print(isGreater)

let isEqual = date1 == date2
print(isEqual)

or alternatively

let result = date1.compare(date2)
switch result {
    case .OrderedAscending     :   print("date 1 is earlier than date 2")
    case .OrderedDescending    :   print("date 1 is later than date 2")
    case .OrderedSame          :   print("two dates are the same")
}

better way creating extension on Date

extension Date {

  fun isGreater(than date: Date) -> Bool {
    return self > date 
  }

  func isSmaller(than date: Date) -> Bool {
    return self < date
  }

  func isEqual(to date: Date) -> Bool {
    return self == date
  }

}

usage let isGreater = date1.isGreater(than: date2)

Diskprotek · Accepted Answer · 2017-03-09 21:42:37Z

3

This function worked for me for comparing whether one date (startDate) was after the endDate where both were defined as NSDate variables:

if startDate.compare(endDate as Date) == ComparisonResult.orderedDescending

answered Mar 9, 2017 at 21:42

Diskprotek

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János · Accepted Answer · 2015-02-13 15:02:35Z

implementation in Swift

let documentsPath = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0] as NSString
let files = NSFileManager.defaultManager().contentsOfDirectoryAtPath(documentsPath, error: nil)

let filesAndProperties = NSMutableArray()
for file in files! {

    let filePath = documentsPath.stringByAppendingString(file as NSString)
    let properties = NSFileManager.defaultManager().attributesOfItemAtPath(filePath, error: nil)
    let modDate = properties![NSFileModificationDate] as NSDate
    filesAndProperties.addObject(NSDictionary(objectsAndKeys: file, "path", modDate, "lastModDate"))
}

let sortedFiles = filesAndProperties.sortedArrayUsingComparator({
    (path1, path2) -> NSComparisonResult in

    var comp = (path1.objectForKey("lastModDate") as NSDate).compare(path2.objectForKey("lastModDate") as NSDate)
    if comp == .OrderedDescending {

        comp = .OrderedAscending
    } else if comp == .OrderedAscending {

        comp = .OrderedDescending
    }

    return comp
})

Trevor Jordet · Accepted Answer · 2016-08-17 21:58:29Z

2

var dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd"
let dateData: String = dateFormatter.stringFromDate(date1)
let testDate: String = dateFormatter.stringFromDate(date2)
print(dateData == testDate)

answered Aug 17, 2016 at 21:58

Trevor Jordet

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larod · Accepted Answer · 2014-10-22 13:34:29Z

1

someArray.sort({($0.dateAdded?.timeIntervalSinceReferenceDate)! < ($1.dateAdded?.timeIntervalSinceReferenceDate)!})

dateAdded is an NSDate variable in my object

class MyClass {
    let dateAdded: NSDate?
}

answered Oct 22, 2014 at 13:34

larod

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Maninderjit Singh · Accepted Answer · 2016-05-23 12:17:30Z

We have scenario to check current time lies b/w two times (two dates).For Example , I want to check the current lie between clinic(Hospital) opening time and closing time.

Use the simple Code.

      NSDate * now = [NSDate date];
        NSDateFormatter *outputFormatter = [[NSDateFormatter alloc] init];
        [outputFormatter setDateFormat:@"HH:mm:ss"];

        //current time
        NSString *currentTimeString = [outputFormatter stringFromDate:now];
        NSDate *dateCurrent = [outputFormatter dateFromString:currentTimeString];


        NSString *timeStart = @"09:00:00";
        NSString *timeEnd = @"22:00:00";

        NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
        [formatter setDateFormat:@"HH:mm:ss"];

        NSDate *dateStart= [formatter timeStart];
        NSDate *dateEnd = [formatter timeEnd];
        NSComparisonResult result = [dateCurrent compare:dateStart];
        NSComparisonResult resultSecond = [date2 compare:dateEnd];

if(result == NSOrderedDescending && resultSecond == NSOrderedDescending)
        {
            NSLog(@"current time lies in starting and end time");
    }else {
            NSLog(@"current time doesn't lie in starting and end time");
        }

Himanshu · Accepted Answer · 2016-12-27 08:52:13Z

1

For swift 3, you can use the below function to compare between two dates.

func compareDate(dateInitial:Date, dateFinal:Date) -> Bool {
    let order = Calendar.current.compare(dateInitial, to: dateFinal, toGranularity: .day)
    switch order {
    case .orderedSame:
        return true
    default:
        return false
    }
}

toGranularity can be changed according to the constraints on which you want to apply your comparison.

answered Dec 27, 2016 at 8:52

Himanshu

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t1ser · Accepted Answer · 2020-12-02 20:14:36Z

To extend on SashaZ - Swift iOS 8 and up

Are these dates from the same day?
Are these dates from the same month?
is this date from a previous month than the other?

When you need more than simply bigger or smaller date comparisons. For example is it the same day or the previous day,...

Note: Never forget the timezone. Calendar timezone has a default, but if you do not like the default, you have to set the timezone yourself. To know which day it is, you need to know in which timezone you are asking.

extension Date {
    func compareTo(date: Date, toGranularity: Calendar.Component ) -> ComparisonResult  {
        var cal = Calendar.current
        cal.timeZone = TimeZone(identifier: "Europe/Paris")!
        return cal.compare(self, to: date, toGranularity: toGranularity)
        }
    }

Use it like this:

if thisDate.compareTo(date: Date(), toGranularity: .day) == .orderedDescending {
// thisDate is a previous day
}

Of a more complex example. Find and filter all dates in an array, which are from the same day as "findThisDay":

let formatter = DateFormatter()
formatter.timeZone = TimeZone(identifier: "Europe/Paris")
formatter.dateFormat = "yyyy/MM/dd HH:mm:ss"

let findThisDay = formatter.date(from: "2018/11/05 08:11:08")!
_ = [
    formatter.date(from: "2018/12/05 08:08:08")!, 
    formatter.date(from: "2018/11/05 08:11:08")!,
    formatter.date(from: "2018/11/05 11:08:22")!,
    formatter.date(from: "2018/11/05 22:08:22")!,
    formatter.date(from: "2018/11/05 08:08:22")!,
    formatter.date(from: "2018/11/07 08:08:22")!,
    ]
    .filter{ findThisDay.compareTo(date: $0 , toGranularity: .day) == .orderedSame }
    .map { print(formatter.string(from: $0)) }

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