Difference in Months between two dates in JavaScript

Question

How would I work out the difference for two Date   objects in JavaScript  while only return the number of months in the difference   Any help would be great

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function monthDiff date1  date2  countDays       countDays    typeof countDays      undefined      countDays   false     if   date1     date2        return 0         let bigDate   date1    let smallDate   date2     if  date1  lt  date2        bigDate   date2      smallDate   date1         let monthsCount    bigDate getFullYear   - smallDate getFullYear      12    bigDate getMonth   - smallDate getMonth        if  countDays  amp  amp  bigDate getDate    lt  smallDate getDate          --monthsCount         return monthsCount

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If you do not consider the day of the month  this is by far the simpler solution   x000D   x000D  function monthDiff dateFrom  dateTo    x000D   return dateTo getMonth   - dateFrom getMonth      x000D      12    dateTo getFullYear   - dateFrom getFullYear     x000D    x000D   x000D   x000D    examples x000D  console log monthDiff new Date 2000  01   new Date 2000  02       1 x000D  console log monthDiff new Date 1999  02   new Date 2000  02       12 full year x000D  console log monthDiff new Date 2009  11   new Date 2010  0       1 x000D   x000D   x000D    Be aware that month index is 0-based  This means that January   0 and December   11

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To expand on  T J  s answer  if you re looking for simple months  rather than full calendar months  you could just check if d2 s date is greater than or equal to than d1 s   That is  if d2 is later in its month than d1 is in its month  then there is 1 more month   So you should be able to just do this   function monthDiff d1  d2        var months      months    d2 getFullYear   - d1 getFullYear      12      months -  d1 getMonth     1      months    d2 getMonth           edit  increment months if d2 comes later in its month than d1 in its month     if  d2 getDate    gt   d1 getDate            months          end edit     return months  lt   0   0   months     monthDiff      new Date 2008  10  4      November 4th  2008     new Date 2010  2  12      March 12th  2010       Result  16  4 Nov     4 Dec  08  4 Dec  08     4 Dec  09  4 Dec  09     4 March  10   This doesn t totally account for time issues  e g  3 March at 4 00pm and 3 April at 3 00pm   but it s more accurate and for just a couple lines of code

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function calcualteMonthYr        var fromDate  new Date     txtDurationFrom2   val       date picker  text fields      var toDate   new Date     txtDurationTo2   val      var months 0          months    toDate getFullYear   - fromDate getFullYear      12          months -  fromDate getMonth            months    toDate getMonth                if  toDate getDate    lt  fromDate getDate                     months--                        txtTimePeriod2   val months

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Any value is returned along with its absolute value  function differenceInMonths firstDate  secondDate        if  firstDate  gt  secondDate   firstDate  secondDate     secondDate  firstDate       let diffMonths    secondDate getFullYear   - firstDate getFullYear      12      diffMonths -  firstDate getMonth        diffMonths    secondDate getMonth        return diffMonths

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This should work fine   function monthDiff d1  d2        var months      months    d2 getFullYear   - d1 getFullYear      12      months    d2 getMonth   - d1 getMonth        return months

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below logic will fetch difference in months   endDate getFullYear   12 endDate getMonth   - startDate getFullYear   12 startDate getMonth

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function monthDiff d1  d2    var months  d1day  d2day  d1new  d2new  diffdate d2month d2year d1maxday d2maxday  months    d2 getFullYear   - d1 getFullYear      12  months -  d1 getMonth     1  months    d2 getMonth    months    months  lt   0   0   months   d1day   d1 getDate    d2day   d2 getDate    if d1day  gt  d2day        d2month   d2 getMonth        d2year   d2 getFullYear        d1new   new Date d2year  d2month-1  d1day 0 0 0 0       var timeDiff   Math abs d2 getTime   - d1new getTime               diffdate   Math abs Math ceil timeDiff    1000   3600   24          d1new   new Date d2year  d2month  1 0 0 0 0       d1new setDate d1new getDate  -1       d1maxday   d1new getDate        months    diffdate   d1maxday    else         if   d1 getMonth      d2 getMonth    amp  amp  d1 getFullYear      d2 getFullYear                   months    1            diffdate   d2day - d1day   1      d2month   d2 getMonth        d2year   d2 getFullYear        d2new   new Date d2year  d2month   1  1  0  0  0  0       d2new setDate d2new getDate  -1       d2maxday   d2new getDate        months    diffdate   d2maxday     return months

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The definition of  the number of months in the difference  is subject to a lot of interpretation   -   You can get the year  month  and day of month from a JavaScript date object  Depending on what information you re looking for  you can use those to figure out how many months are between two points in time   For instance  off-the-cuff   function monthDiff d1  d2        var months      months    d2 getFullYear   - d1 getFullYear      12      months -  d1 getMonth        months    d2 getMonth        return months  lt   0   0   months       x000D   x000D  function monthDiff d1  d2    x000D      var months  x000D      months    d2 getFullYear   - d1 getFullYear      12  x000D      months -  d1 getMonth    x000D      months    d2 getMonth    x000D      return months  lt   0   0   months  x000D    x000D   x000D  function test d1  d2    x000D      var diff   monthDiff d1  d2   x000D      console log  x000D          d1 toISOString   substring 0  10   x000D           to   x000D          d2 toISOString   substring 0  10   x000D               x000D          diff x000D         x000D    x000D   x000D  test  x000D      new Date 2008  10  4      November 4th  2008 x000D      new Date 2010  2  12      March 12th  2010 x000D     x000D     Result  16 x000D   x000D  test  x000D      new Date 2010  0  1       January 1st  2010 x000D      new Date 2010  2  12      March 12th  2010 x000D     x000D     Result  2 x000D   x000D  test  x000D      new Date 2010  1  1       February 1st  2010 x000D      new Date 2010  2  12      March 12th  2010 x000D     x000D     Result  1 x000D   x000D   x000D     Note that month values in JavaScript start with 0   January    Including fractional months in the above is much more complicated  because three days in a typical February is a larger fraction of that month   10 714   than three days in August   9 677    and of course even February is a moving target depending on whether it s a leap year   There are also some date and time libraries available for JavaScript that probably make this sort of thing easier     Note  There used to be a   1 in the above  here   months    d2 getFullYear   - d1 getFullYear      12  months -  d1 getMonth     1     --------------------     months    d2 getMonth      That s because originally I said         this finds out how many full months lie between two dates  not counting partial months  e g   excluding the month each date is in     I ve removed it for two reasons    Not counting partial months turns out not to be what many  most   people coming to the answer want  so I thought I should separate them out  It didn t always work even by that definition   -D  Sorry

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One approach would be to write a simple Java Web Service  REST JSON  that uses JODA library  http   joda-time sourceforge net faq html datediff  to calculate difference between two dates and call that service from javascript   This assumes your back end is in Java

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It also counts the days and convert them in months    function monthDiff d1  d2        var months      months    d2 getFullYear   - d1 getFullYear      12      calculates months between two years     months -  d1 getMonth     1       months    d2 getMonth       calculates number of complete months between two months     day1   30-d1 getDate          day2   day1   d2 getDate        months    parseInt day2 30      calculates no of complete months lie between two dates     return months  lt   0   0   months     monthDiff      new Date 2017  8  8      Aug 8th  2017     d1      new Date 2017  12  12      Dec 12th  2017    d2       return value will be 4 months

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Following code returns full months between two dates by taking nr of days of partial months into account as well   var monthDiff   function d1  d2      if  d2  lt  d1          var dTmp   d2      d2   d1      d1   dTmp         var months    d2 getFullYear   - d1 getFullYear      12    months -  d1 getMonth     1    months    d2 getMonth       if  d1 getDate    lt   d2 getDate     months    1     return months     monthDiff new Date 2015  01  20   new Date 2015  02  20    gt  1  monthDiff new Date 2015  01  20   new Date 2015  02  19    gt  0  monthDiff new Date 2015  01  20   new Date 2015  01  22    gt  0

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Consider each date in terms of months  then subtract to find the difference   var past date   new Date  11 1 2014    var current date   new Date     var difference    current date getFullYear   12   current date getMonth    -  past date getFullYear   12   past date getMonth       This will get you the difference of months between the two dates  ignoring the days

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Sometimes you may want to get just the quantity of the months between two dates totally ignoring the day part  So for instance  if you had two dates- 2013 06 21 and 2013 10 18- and you only cared about the 2013 06 and 2013 10 parts  here are the scenarios and possible solutions   var date1 new Date 2013 5 21    Remember  months are 0 based in JS var date2 new Date 2013 9 18   var year1 date1 getFullYear    var year2 date2 getFullYear    var month1 date1 getMonth    var month2 date2 getMonth    if month1   0     Have to take into account   month1      month2      var numberOfMonths     1 If you want just the number of the months between the two dates excluding both month1 and month2  numberOfMonths    year2 - year1    12    month2 - month1  - 1    2 If you want to include either of the months  numberOfMonths    year2 - year1    12    month2 - month1     3 If you want to include both of the months  numberOfMonths    year2 - year1    12    month2 - month1    1

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I like not to reinvent a wheel keep it simple  I mean not to care about the number of days in months  the leap year  etc   and use date-fns lib  thus  npm install -s date-fns  and const differenceInMonths   require  date-fns differenceInMonths           gt        console log differenceInMonths new Date  2015-12-01    new Date  2013-12-01         console log differenceInMonths new Date 1582261140000   new Date  2014-12-01         console log differenceInMonths new Date 1582261140000   new Date 1573621200000

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Calculate the difference between two dates include fraction of month  days      var difference    date2 getDate   - date1 getDate      30       date2 getMonth   - date1 getMonth          12    date2 getFullYear   - date1 getFullYear           For example    date1  24 09 2015  24th Sept 2015    date2  09 11 2015  9th Nov 2015    the difference  2 5  months

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Here you go other approach with less looping   calculateTotalMonthsDifference   function firstDate  secondDate            var fm   firstDate getMonth            var fy   firstDate getFullYear            var sm   secondDate getMonth            var sy   secondDate getFullYear            var months   Math abs   fy - sy    12    fm - sm           var firstBefore   firstDate  gt  secondDate          firstDate setFullYear sy           firstDate setMonth sm           firstBefore   firstDate  lt  secondDate   months--        secondDate  lt  firstDate   months--               return months

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There are two approaches  mathematical  amp  quick  but subject to vagaries in the calendar  or iterative  amp  slow  but handles all the oddities  or at least delegates handling them to a well-tested library    If you iterate through the calendar  incrementing the start date by one month  amp  seeing if we pass the end date  This delegates anomaly-handling to the built-in Date   classes  but could be slow IF you re doing this for a large number of dates  James  answer takes this approach  As much as I dislike the idea  I think this is the  safest  approach  and if you re only doing one calculation  the performance difference really is negligible  We tend to try to over-optimize tasks which will only be performed once   Now  if you re calculating this function on a dataset  you probably don t want to run that function on each row  or god forbid  multiple times per record   In that case  you can use almost any of the other answers here except the accepted answer  which is just wrong  difference between new Date   and new Date   is -1     Here s my stab at a mathematical-and-quick approach  which accounts for differing month lengths and leap years  You really should only use a function like this if you ll be applying this to a dataset  doing this calculation over  amp  over   If you just need to do it once  use James  iterative approach above  as you re delegating handling all the  many  exceptions to the Date   object   function diffInMonths from  to       var months   to getMonth   - from getMonth      12    to getFullYear   - from getFullYear           if to getDate    lt  from getDate             var newFrom   new Date to getFullYear   to getMonth   from getDate             if  to  lt  newFrom   amp  amp  to getMonth      newFrom getMonth    amp  amp  to getYear    4    0               months--                       return months

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You could also consider this solution  this function returns the month difference in integer or number   Passing the start date as the first or last param  is fault tolerant  Meaning  the function would still return the same value    x000D   x000D  const diffInMonths    end  start    gt    x000D     var timeDiff   Math abs end getTime   - start getTime     x000D     return Math round timeDiff    2e3   3600   365 25    x000D    x000D   x000D  const result   diffInMonths new Date 2015  3  28   new Date 2010  1  25    x000D   x000D     shows month difference as integer number x000D  console log result   x000D   x000D   x000D

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Here s a function that accurately provides the number of months between 2 dates  The default behavior only counts whole months  e g  3 months and 1 day will result in a difference of 3 months  You can prevent this by setting the roundUpFractionalMonths param as true  so a 3 month and 1 day difference will be returned as 4 months   The accepted answer above  T J  Crowder s answer  isn t accurate  it returns wrong values sometimes   For example  monthDiff new Date  Jul 01  2015    new Date  Aug 05  2015    returns 0 which is obviously wrong  The correct difference is either 1 whole month or 2 months rounded-up   Here s the function I wrote   function getMonthsBetween date1 date2 roundUpFractionalMonths          Months will be calculated between start and end dates        Make sure start date is less than end date        But remember if the difference should be negative      var startDate date1      var endDate date2      var inverse false      if date1 gt date2                startDate date2          endDate date1          inverse true               Calculate the differences between the start and end dates     var yearsDifference endDate getFullYear  -startDate getFullYear        var monthsDifference endDate getMonth  -startDate getMonth        var daysDifference endDate getDate  -startDate getDate         var monthCorrection 0        If roundUpFractionalMonths is true  check if an extra month needs to be added from rounding up        The difference is done by ceiling  round up   e g  3 months and 1 day will be 4 months      if roundUpFractionalMonths   true  amp  amp  daysDifference gt 0                monthCorrection 1              If the day difference between the 2 months is negative  the last month is not a whole month      else if roundUpFractionalMonths   true  amp  amp  daysDifference lt 0                monthCorrection -1             return  inverse -1 1   yearsDifference 12 monthsDifference monthCorrection

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Difference in Months between two dates in JavaScript    start date   new Date year  month  day     Create start date object by passing appropiate argument  end date   new Date new Date year  month  day    total months between start date and end date     total months    end date getFullYear   - start date getFullYear    12    end date getMonth   - start date getMonth

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getMonthDiff d1  d2        var year1   dt1 getFullYear        var year2   dt2 getFullYear        var month1   dt1 getMonth        var month2   dt2 getMonth        var day1   dt1 getDate        var day2   dt2 getDate        var months   month2 - month1      var years   year2 -year1     days   day2 - day1      if  days  lt  0            months -  1            if  months  lt  0            months    12            return months   years  2

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anyVar      DisplayTo getFullYear     12    DisplayTo getMonth    -   DisplayFrom getFullYear     12    DisplayFrom getMonth

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I know this is really late  but posting it anyway just in case it helps others  Here is a function I came up with that seems to do a good job of counting differences in months between two dates  It is admittedly a great deal raunchier than Mr Crowder s  but provides more accurate results by stepping through the date object  It is in AS3 but you should just be able to drop the strong typing and you ll have JS  Feel free to make it nicer looking anyone out there       function countMonths   startDate Date  endDate Date   int               var stepDate Date   new Date          stepDate time   startDate time          var monthCount int           while  stepDate time  lt   endDate time                  stepDate month    1              monthCount    1                                if   stepDate    endDate                  monthCount -  1                     return monthCount

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See what I use   function monthDiff         var startdate   Date parseExact     startingDate   val     dd MM yyyy        var enddate   Date parseExact     endingDate   val     dd MM yyyy        var months   0      while  startdate  lt  enddate            if  startdate getMonth       1  amp  amp  startdate getDate       28                months                startdate addMonths 1               startdate addDays 2             else               months                startdate addMonths 1                       return months

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If you need to count full months  regardless of the month being 28  29  30 or 31 days  Below should work    var months   to getMonth   - from getMonth           12    to getFullYear   - from getFullYear       if to getDate    lt  from getDate         months--    return months    This is an extended version of the answer https   stackoverflow com a 4312956 1987208 but fixes the case where it calculates 1 month for the case from 31st of January to 1st of February  1day    This will cover the following    1st Jan to 31st Jan ---  30days ---  will result in 0  logical since it is not a full month  1st Feb to 1st Mar ---  28 or 29 days ---  will result in 1  logical since it is a full month  15th Feb to 15th Mar ---  28 or 29 days ---  will result in 1  logical since a month passed  31st Jan to 1st Feb ---  1 day ---  will result in 0  obvious but the mentioned answer in the post results in 1 month

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Number Of Months When Day  amp  Time Doesn t Matter In this case  I m not concerned with full months  part months  how long a month is  etc  I just need to know the number of months  A relevant real world case would be where a report is due every month  and I need to know how many reports there should be  Example   January   1 month January - February   2 months November - January   3 months  This is an elaborated code example to show where the numbers are going  Let s take 2 timestamps that should result in 4 months  November 13  2019 s timestamp  1573621200000 February 20  2020 s timestamp  1582261140000  May be slightly different with your timezone   time pulled  The day  minutes  and seconds don t matter and can be included in the timestamp  but we will disregard it with our actual calculation  Step 1  convert the timestamp to a JavaScript date let dateRangeStartConverted   new Date 1573621200000   let dateRangeEndConverted   new Date 1582261140000    Step 2  get integer values for the months   years let startingMonth   dateRangeStartConverted getMonth    let startingYear   dateRangeStartConverted getFullYear    let endingMonth   dateRangeEndConverted getMonth    let endingYear   dateRangeEndConverted getFullYear     This gives us  Starting month   11 Starting Year   2019 Ending month   2 Ending Year   2020  Step 3  Add  12    endYear - startYear     1 to the ending month   This makes our starting month stay at 11 This makes our ending month equal 15 2    12    2020 - 2019     1   15  Step 4  Subtract the months 15 - 11   4  we get our 4 month result  29 Month Example Example November 2019 through March 2022 is 29 months  If you put these into an excel spreadsheet  you will see 29 rows   Our starting month is 11 Our ending month is 40 3    12    2022-2019     1  40 - 11   29

[javascript] Difference in Months between two dates in JavaScript

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