How to compare two NSDates Which is more recent

Question

I am trying to achieve a dropBox sync and need to compare the dates of two files  One is on my dropBox account and one is on my iPhone    I came up with the following  but I get unexpected results  I guess I m doing something fundamentally wrong when comparing the two dates  I simply used the    lt  operators  but I guess this is no good as I am comparing two NSDate strings  Here we go   NSLog   dB   lastModified       dbObject lastModifiedDate    NSLog   iP   lastModified        self getDateOfLocalFile   NoteBook txt      if   dbObject lastModifiedDate   lt   self getDateOfLocalFile   NoteBook txt          NSLog      db is more up-to-date  Download in progress            self DBdownload   NoteBook txt        NSLog   Download complete       else       NSLog      iP is more up-to-date  Upload in progress            self DBupload   NoteBook txt        NSLog   Upload complete         This gave me the following  random  amp  wrong  output   2011-05-11 14 20 54 413 NotePage 6918 207  dB   lastModified  2011-05-11 13 18 25  0000 2011-05-11 14 20 54 414 NotePage 6918 207  iP   lastModified  2011-05-11 13 20 48  0000 2011-05-11 14 20 54 415 NotePage 6918 207     db is more up-to-date    or this one which happens to be correct   2011-05-11 14 20 25 097 NotePage 6903 207  dB   lastModified  2011-05-11 13 18 25  0000 2011-05-11 14 20 25 098 NotePage 6903 207  iP   lastModified  2011-05-11 13 19 45  0000 2011-05-11 14 20 25 099 NotePage 6903 207     iP is more up-to-date

User · Answer

Some date utilities  including comparisons IN ENGLISH  which is nice    import  lt Foundation Foundation h gt     interface NSDate  Util   - BOOL  isLaterThanOrEqualTo  NSDate  date  - BOOL  isEarlierThanOrEqualTo  NSDate  date  - BOOL  isLaterThan  NSDate  date  - BOOL  isEarlierThan  NSDate  date  -  NSDate   dateByAddingDays  int days    end   The implementation    import  NSDate Util h     implementation NSDate  Util   - BOOL  isLaterThanOrEqualTo  NSDate  date       return    self compare date     NSOrderedAscending      - BOOL  isEarlierThanOrEqualTo  NSDate  date       return    self compare date     NSOrderedDescending     - BOOL  isLaterThan  NSDate  date       return   self compare date     NSOrderedDescending      - BOOL  isEarlierThan  NSDate  date       return   self compare date     NSOrderedAscending      -  NSDate    dateByAddingDays  int days       NSDate  retVal      NSDateComponents  components     NSDateComponents alloc  init        components setDay days        NSCalendar  gregorian     NSCalendar alloc  initWithCalendarIdentifier NSGregorianCalendar       retVal    gregorian dateByAddingComponents components toDate self options 0       return retVal      end

User · Answer

In Swift  you can overload existing operators   func  gt   lhs  NSDate  rhs  NSDate  - gt  Bool       return lhs timeIntervalSinceReferenceDate  gt  rhs timeIntervalSinceReferenceDate    func  lt   lhs  NSDate  rhs  NSDate  - gt  Bool       return lhs timeIntervalSinceReferenceDate  lt  rhs timeIntervalSinceReferenceDate     Then  you can compare NSDates directly with  lt    gt   and     already supported

User · Answer

Use this simple function for date comparison  - BOOL dateComparision  NSDate  date1 andDate2  NSDate  date2   BOOL isTokonValid   if   date1 compare date2     NSOrderedDescending        NSLog   date1 is later than date2        isTokonValid   YES    else if   date1 compare date2     NSOrderedAscending        NSLog   date1 is earlier than date2        isTokonValid   NO    else       isTokonValid   NO      NSLog   dates are the same       return isTokonValid

User · Answer

You can compare two date by this method also          switch   currenttimestr  compare endtimestr                         case NSOrderedAscending                      dateOne is earlier in time than dateTwo                 break               case NSOrderedSame                      The dates are the same                 break              case NSOrderedDescending                      dateOne is later in time than dateTwo                   break

User · Answer

NSDate has a compare function   compare  Returns an NSComparisonResult value that indicates the temporal ordering of the receiver and another given date    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 Mac OS X   Return Value    If the receiver and anotherDate are exactly equal to each other  NSOrderedSame If the receiver is later in time than anotherDate  NSOrderedDescending If the receiver is earlier in time than anotherDate  NSOrderedAscending

User · Answer

You want to use the NSDate compare   laterDate   earlierDate   or isEqualToDate  methods   Using the  lt  and   operators in this situation is comparing the pointers  not the dates

User · Answer

Late to the party  but another easy way of comparing NSDate objects is to convert them into primitive types which allows for easy use of       lt        etc  eg   if   dateA timeIntervalSinceReferenceDate   gt   dateB timeIntervalSinceReferenceDate           do stuff     timeIntervalSinceReferenceDate converts the date into seconds since the reference date  1 January 2001  GMT    As timeIntervalSinceReferenceDate returns a NSTimeInterval  which is a double typedef   we can use primitive comparators

User · Answer

I have tried it hope it works for you     NSCalendar  gregorian     NSCalendar alloc  initWithCalendarIdentifier NSGregorianCalendar         int unitFlags  NSDayCalendarUnit        NSDateFormatter  dateFormatter      NSDateFormatter alloc  init  autorelease        NSDate  myDate        NSDate alloc  init         dateFormatter setDateFormat   dd-MM-yyyy       myDate    dateFormatter dateFromString self strPrevioisDate        NSDateComponents  comps    gregorian components unitFlags fromDate myDate toDate  NSDate date  options 0      NSInteger day  comps day

User · Answer

Why don t you guys use these NSDate compare methods   -  NSDate   earlierDate  NSDate   anotherDate  -  NSDate   laterDate  NSDate   anotherDate

User · Answer

Let s assume two dates   NSDate  date1  NSDate  date2    Then the following comparison will tell which is earlier later same   if   date1 compare date2     NSOrderedDescending        NSLog   date1 is later than date2      else if   date1 compare date2     NSOrderedAscending        NSLog   date1 is earlier than date2      else       NSLog   dates are the same        Please refer to the NSDate class documentation for more details

User · Answer

You should use    -  NSComparisonResult compare  NSDate   anotherDate   to compare dates  There is no operator overloading in objective C

User · Answer

-  NSDate   earlierDate  NSDate   anotherDate   This returns the earlier of the receiver and anotherDate  If both are same  the receiver is returned

User · Answer

I have encounter almost same situation  but in my case I m checking if number of days difference  NSCalendar  cal    NSCalendar currentCalendar   NSDateComponents  compDate    cal components NSDayCalendarUnit fromDate fDate toDate tDate options 0   int numbersOfDaysDiff    compDate day  1     do what ever comparison logic with this int    Useful when you need to compare NSDate in Days Month Year unit

[iphone] How to compare two NSDates: Which is more recent?

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