How can I calculate the number of years between two dates

Question

I want to get the number of years between two dates  I can get the number of days between these two days  but if I divide it by 365 the result is incorrect because some years have 366 days   This is my code to get date difference   var birthday   value   format 01 02 1900 var dateParts   birthday split        var checkindate   new Date dateParts 2   dateParts 0  - 1  dateParts 1       var now   new Date    var difference   now - checkindate  var days   difference    1000 60 60 24    var thisyear   new Date   getFullYear    var birthyear   dateParts 2        var number of long years   0  for var y birthyear  y  lt   thisyear  y             if   y   4    0  amp  amp  y   100    0     y   400    0                          number of long years                              The day count works perfectly  I am trying to do add the additional days when it is a 366-day year  and I m doing something like this    var years     days   thisyear-birthyear                  number of long years 366      thisyear-birthyear-number of long years  365       I m getting the year count   Is this correct  or is there a better way to do this

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Little out of date but here is a function you can use   function calculateAge birthMonth  birthDay  birthYear        var currentDate   new Date        var currentYear   currentDate getFullYear        var currentMonth   currentDate getMonth        var currentDay   currentDate getDate         var calculatedAge   currentYear - birthYear       if  currentMonth  lt  birthMonth - 1            calculatedAge--            if  birthMonth - 1    currentMonth  amp  amp  currentDay  lt  birthDay            calculatedAge--            return calculatedAge     var age   calculateAge 12  8  1993   alert age

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Date calculation work via the Julian day number  You have to take the first of January of the two years  Then you convert the Gregorian dates into Julian day numbers and after that you take just the difference

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function dateDiffYearsOnly  dateNew dateOld       function date2ymd d   w new Date d  return  w getFullYear   w getMonth   w getDate        function ymd2N y  return    y 0  lt  lt 4  y 1   lt  lt 5  y 2      or 60 and 60    or 13 and 32    or 25 and 40      with        function date2N d   return ymd2N date2ymd d        return   date2N dateNew -date2N dateOld   gt  gt 9    test  dateDiffYearsOnly Date now   new Date Date now  -7 366 24 3600 1000    dateDiffYearsOnly Date now   new Date Date now  -7 365 24 3600 1000

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if someone needs for interest calculation year in float format  function floatYearDiff olddate  newdate      var new y   newdate getFullYear      var old y   olddate getFullYear      var diff y   new y - old y    var start year   new Date olddate     var end year   new Date olddate     start year setFullYear new y     end year setFullYear new y 1     if  start year  gt  newdate        start year setFullYear new y-1       end year setFullYear new y       diff y--        var diff   diff y    newdate - start year   end year - start year     return diff

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You can get the exact age using timesstamp   const getAge    dateOfBirth  dateToCalculate   new Date      gt        const dob   new Date dateOfBirth  getTime        const dateToCompare   new Date dateToCalculate  getTime        const age    dateToCompare - dob     365   24   60   60   1000       return Math floor age

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Maybe my function can explain better how to do this in a simple way without loop  calculations and or libs   x000D   x000D  function checkYearsDifference birthDayDate   x000D      var todayDate   new Date    x000D      var thisMonth   todayDate getMonth    x000D      var thisYear   todayDate getFullYear    x000D      var thisDay   todayDate getDate    x000D      var monthBirthday   birthDayDate getMonth     x000D      var yearBirthday   birthDayDate getFullYear    x000D      var dayBirthday   birthDayDate getDate    x000D        first just make the difference between years x000D      var yearDifference   thisYear - yearBirthday  x000D        then check months x000D      if  thisMonth    monthBirthday   x000D          if months are the same then check days x000D        if  thisDay lt dayBirthday   x000D            if today day is before birthday day x000D            then I have to remove 1 year x000D             no birthday yet  x000D          yearDifference   yearDifference -1  x000D          x000D          if not no action because year difference is ok x000D        x000D      else   x000D        if  thisMonth  lt  monthBirthday    x000D            if actual month is before birthday one x000D            then I have to remove 1 year x000D          yearDifference   yearDifference -1  x000D          x000D          if not no action because year difference is ok x000D        x000D      return yearDifference  x000D      x000D   x000D   x000D

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getAge month  day  year        let yearNow   new Date   getFullYear        let monthNow   new Date   getMonth     1      let dayNow   new Date   getDate        if  monthNow     month  amp  amp  dayNow  lt  day    monthNow  lt  month          return yearNow - year - 1        else         return yearNow - year

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let currentTime   new Date   getTime    let birthDateTime  new Date birthDate  getTime    let difference    currentTime - birthDateTime  var ageInYears difference  1000 60 60 24 365

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No for-each loop  no extra jQuery plugin needed    Just call the below function   Got from Difference between two dates in years          function dateDiffInYears dateold  datenew                var ynew   datenew getFullYear                var mnew   datenew getMonth                var dnew   datenew getDate                var yold   dateold getFullYear                var mold   dateold getMonth                var dold   dateold getDate                var diff   ynew - yold              if  mold  gt  mnew  diff--              else                   if  mold    mnew                        if  dold  gt  dnew  diff--                                              return diff

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This one Help you              id  btnSubmit    click function              debugger         var SDate       id  txtStartDate    val   split  -            var Smonth   SDate 0           var Sday   SDate 1           var Syear   SDate 2              alert Syear   alert Sday   alert Smonth           var EDate       id  txtEndDate    val   split  -            var Emonth   EDate 0           var Eday   EDate 1           var Eyear   EDate 2           var y   parseInt Eyear  - parseInt Syear           var m  d          if   parseInt Emonth  - parseInt Smonth    gt  0                m   parseInt Emonth  - parseInt Smonth                     else               m   parseInt Emonth    12 - parseInt Smonth               y   y - 1                    if   parseInt Eday  - parseInt Sday    gt  0                d   parseInt Eday  - parseInt Sday                     else               d   parseInt Eday    30 - parseInt Sday               m   m - 1                       alert y         m         d               id  lblAge    text  your age is     y    years      m    month      d    days            return false

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function getYearDiff startDate  endDate        let yearDiff   endDate getFullYear   - startDate getFullYear        if  startDate getMonth    gt  endDate getMonth              yearDiff--        else if  startDate getMonth       endDate getMonth              if  startDate getDate    gt  endDate getDate                  yearDiff--            else if  startDate getDate       endDate getDate                  if  startDate getHours    gt  endDate getHours                      yearDiff--                else if  startDate getHours       endDate getHours                      if  startDate getMinutes    gt  endDate getMinutes                          yearDiff--                                                      return yearDiff     alert getYearDiff firstDate  secondDate

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If you are using moment          Convert date of birth into age    param  string  dateOfBirth - date of birth    param  string  dateToCalculate  -  date to compare    returns  number  - age     function getAge dateOfBirth  dateToCalculate        const dob   moment dateOfBirth       return moment dateToCalculate  diff dob   years

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Using pure javascript Date    we can calculate the numbers of years like below   x000D   x000D  document getElementById  getYearsBtn   addEventListener  click   function      x000D    var enteredDate   document getElementById  sampleDate   value  x000D       Below one is the single line logic to calculate the no  of years    x000D    var years   new Date new Date   - new Date enteredDate   getFullYear   - 1970  x000D    console log years   x000D      x000D   lt input type  text  id  sampleDate  value  1980 01 01  gt  x000D   lt div gt Format  yyyy-mm-dd or yyyy mm dd lt  div gt  lt br gt  x000D   lt button id  getYearsBtn  gt Calculate Years lt  button gt  x000D   x000D   x000D

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for var y birthyear  y  lt   thisyear  y       if   y   4    0  amp  amp  y   100    0     y   400    0       days   days-366   number of long years       else       days days-365     year           can you try this way

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Yep  moment js is pretty good for this   var moment   require  moment    var startDate   new Date    var endDate   new Date    endDate setDate endDate getFullYear     5      Add 5 years to second date console log moment duration endDate - startDate  years        This should returns 5

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getYears date1  date2    let years   new Date date1  getFullYear   - new Date date2  getFullYear    let month   new Date date1  getMonth   - new Date date2  getMonth    let dateDiff   new Date date1  getDay   - new Date date2  getDay    if  dateDiff  lt  0        month -  1    if  month  lt  0        years -  1    return years

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Bro  moment js is awesome for this  The diff method is what you want  http   momentjs com docs   displaying difference   The below function return array of years from the year to the current year    x000D   x000D  const getYears    from   2017    gt    x000D    const diff   moment new Date    diff new Date  01 01   from      years     x000D    return     Array diff  gt   0   diff   1   0  keys    map  num    gt    x000D      return from   num  x000D        x000D    x000D   x000D  console log getYears 2016    x000D   lt script src  https   momentjs com downloads moment js  gt  lt  script gt  x000D   x000D   x000D

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Probably not the answer you re looking for  but at 2 6kb  I would not try to reinvent the wheel and I d use something like moment js  Does not have any dependencies   The diff method is probably what you want  http   momentjs com docs   displaying difference

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I use the following for age calculation   I named it gregorianAge   because this calculation gives exactly how we denote age using Gregorian calendar  i e  Not counting the end year if month and day is before the month and day of the birth year    x000D   x000D      x000D     Calculates human age in years given a birth day  Optionally ageAtDate x000D     can be provided to calculate age at a specific date x000D     x000D      param string Date Object birthDate x000D      param string Date Object ageAtDate optional x000D      returns integer Age between birthday and a given date or today x000D      x000D  gregorianAge   function birthDate  ageAtDate    x000D       convert birthDate to date object if already not x000D    if  Object prototype toString call birthDate        object Date    x000D      birthDate   new Date birthDate   x000D   x000D       use today s date if ageAtDate is not provided x000D    if  typeof ageAtDate     undefined   x000D      ageAtDate   new Date    x000D   x000D       convert ageAtDate to date object if already not x000D    else if  Object prototype toString call ageAtDate        object Date    x000D      ageAtDate   new Date ageAtDate   x000D   x000D       if conversion to date object fails return null x000D    if  ageAtDate    null    birthDate    null  x000D      return null  x000D   x000D   x000D    var  m   ageAtDate getMonth   - birthDate getMonth    x000D   x000D       answer  ageAt year minus birth year less one  1  if month and day of x000D       ageAt year is before month and day of birth year x000D    return  ageAtDate getFullYear    - birthDate getFullYear   x000D      -    m  lt  0      m     0  amp  amp  ageAtDate getDate    lt  birthDate getDate     1 0  x000D    x000D   lt input type  text  id  birthDate  value  12 February 1982  gt  x000D   lt div style  font-size  small  color  grey  gt Enter a date in an acceptable format e g  10 Dec 2001 lt  div gt  lt br gt  x000D   lt button onClick  js alert gregorianAge document getElementById  birthDate   value    gt What s my age  lt  button gt  x000D   x000D   x000D

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Sleek foundation javascript function    function calculateAge birthday       birthday is a date    var ageDifMs   Date now   - birthday     var ageDate   new Date ageDifMs      miliseconds from epoch    return Math abs ageDate getUTCFullYear   - 1970

[javascript] How can I calculate the number of years between two dates?

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