How to add subtract dates with JavaScript

Question

I want to let users easily add and subtract dates using JavaScript in order to browse their entries by date   The dates are in the format   mm dd yyyy   I want them to be able to click a  Next  button  and if the date is    06 01 2012  then on clicking next  it should become   06 02 2012   If they click the  prev  button then it should become   05 31 2012    It needs to keep track of leap years  number of days in the month  etc   Any ideas   P S using AJAX to get the date from the server isn t an option  its a bit laggy and not the experience for the user that the client wants

User · Answer

startdate setDate startdate getDate   - daysToSubtract     startdate setDate startdate getDate     daysToAdd

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The JavaScript Date object can help here   The first step is to convert those strings to Date instances  That s easily done   var str    06 07 2012      E g    mm dd yyyy   var dt   new Date parseInt str substring 6   10             Year                   parseInt str substring 0  2   10  - 1     Month  0-11                    parseInt str substring 3  5   10          Day   Then you can do all sorts of useful calculations  JavaScript dates understand leap years and such  They use an idealized concept of  day  which is exactly 86 400 seconds long  Their underlying value is the number of milliseconds since The Epoch  midnight  Jan 1st  1970   it can be a negative number for dates prior to The Epoch   More on the MDN page on Date   You might also consider using a library like MomentJS  which will help with parsing  doing date math  formatting

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Something I am using  jquery needed   in my script I need it for the current day  but of course you can edit it accordingly   HTML    lt label gt Date  lt  label gt  lt input name  date  id  dateChange  type  date   gt   lt input id  SubtractDay  type  button  value  -    gt   lt input id  AddDay  type  button  value       gt    JavaScript       var counter   0       SubtractDay   click function         counter--      var today   new Date        today setDate today getDate     counter       var formattedDate   new Date today       var d     0    formattedDate getDate    slice -2       var m     0     formattedDate getMonth     1   slice -2       var y   formattedDate getFullYear            dateChange   val d         m         y           AddDay   click function         counter        var today   new Date        today setDate today getDate     counter       var formattedDate   new Date today       var d     0    formattedDate getDate    slice -2       var m     0     formattedDate getMonth     1   slice -2       var y   formattedDate getFullYear            dateChange   val d         m         y         jsfiddle

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You can use the native javascript Date object to keep track of dates  It will give you the current date  let you keep  track of calendar specific stuff and even help you manage different timezones  You can add and substract days hours seconds to change the date you are working with or to calculate new dates  take a look at this object reference to learn more  Date Hope that helps

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Working with dates in javascript is always a bit of a hassle  I always end up using a library  Moment js and XDate are both great   http   momentjs com   http   arshaw com xdate   Fiddle   http   jsfiddle net 39fWa   var  output       output        tomorrow   moment   add  days   1        lt pre   gt    appendTo  output  text tomorrow    tomorrow   new XDate   addDays -1        lt pre   gt    appendTo  output  text tomorrow

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The best date utility I ve used is date-fns for a few reasons    Uses the native JavaScript Date format  Immutable  built using pure functions and always returns a new date instance instead of changing the passed one  Modular  import just the functions you need    Package manager    date-fns     1 30 1   Code   import   addDays  subDays   from  date-fns   let today   new Date   let yesterday   subDays today  1  let tomorrow   addDays today  1    Simple and awesome

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var date   new Date  your date string here       e g   2017-11-21   var newdate   new Date date getTime     24 60 60 1000   days     days is the number of days you want to shift the date by   This is the only solution that works reliably when adding subtracting across months and years  Realized this after spending way too much time mucking around with the getDate and setDate methods  trying to adjust for month year shifts   decasteljau  in this thread  has already answered this but just want to emphasize the utility of this method because 90  of the answers out there recommend the getDate and setDate approach

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May be this could help       lt script type  text javascript  language  javascript  gt          function AddDays toAdd                if   toAdd    toAdd          isNaN toAdd   return              var d   new Date                d setDate d getDate     parseInt toAdd                 document getElementById  result   innerHTML   d getDate           d getMonth           d getFullYear               function SubtractDays toAdd                if   toAdd    toAdd          isNaN toAdd   return              var d   new Date                d setDate d getDate   - parseInt toAdd                 document getElementById  result   innerHTML   d getDate           d getMonth           d getFullYear                   lt  script gt      ---------------------- UI ---------------          lt div id  result  gt           lt  div gt           lt input type  text  value  0  onkeyup  AddDays this value      gt           lt input type  text  value  0  onkeyup  SubtractDays this value      gt

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Code    x000D   x000D  var date   new Date  2011    01    02    x000D  alert  the original date is     date   x000D  var newdate   new Date date   x000D   x000D  newdate setDate newdate getDate   - 7      minus the date x000D   x000D  var nd   new Date newdate   x000D  alert  the new date is     nd   x000D   x000D   x000D    Using Datepicker       in   datepicker       minDate  0      onSelect  function dateText  inst           var actualDate   new Date dateText          var newDate   new Date actualDate getFullYear    actualDate getMonth    actualDate getDate   1               out   datepicker  option    minDate   newDate                   out   datepicker       JSFiddle Demo  Extra stuff that might come handy   getDate     Returns the day of the month  from 1-31  getDay      Returns the day of the week  from 0-6  getFullYear     Returns the year  four digits  getHours    Returns the hour  from 0-23  getMilliseconds     Returns the milliseconds  from 0-999  getMinutes      Returns the minutes  from 0-59  getMonth    Returns the month  from 0-11  getSeconds      Returns the seconds  from 0-59    Good link  MDN Date

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In order to get yesterday s date in mm dd yyyy    function gimmeYesterday toAdd                if   toAdd    toAdd          isNaN toAdd   return              var d   new Date                d setDate d getDate   - parseInt toAdd    var yesterDAY    d getMonth    1          d getDate           d getFullYear        endDate   html yesterDAY               document  ready function     gimmeYesterday 1         you can try here  http   jsfiddle net ZQAHE

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The way I like  is if you have a date object you can subtract another date object from it to get the difference  Date objects are based on milliseconds from a certain date    var date1   new Date 2015  02  18       18 03 2015   month is 0-index var date2   new Date 2015  02  20       20 03 2015   var msDiff   date2 - date1     172800000  this is time in milliseconds var daysDiff   msDiff   1000   60   60   24     2 days   So this is how you subtract dates  Now if you want to add them  date1   date2 gives an error   But if I want to get the time in ms I can use   var dateMs   date1 - 0     say I want to add 5 days I can use var days   5  var msToAdd   days   24   60   60   1000   var newDate   new Date dateMs   msToAdd     By subtracting 0 you turn the date object into the milliseconds format

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You need to use getTime   and setTime   to add or substract the time in a javascript Date object   Using setDate   and getDate   will lead to errors when reaching the limits of the months 1  30  31  etc    Using setTime allows you to set an offset in milliseconds  and let the Date object figure the rest   var now new Date    var yesterdayMs   now getTime   - 1000 60 60 24 1     Offset by one day  now setTime  yesterdayMs

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All these functions for adding date are wrong  You are passing the wrong month to the Date function  More information about the problem    http   www domdigger com blog  p 9

[javascript] How to add/subtract dates with JavaScript?

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