javascript - How to get first date and last date of the week from week number and year? - Stack Overflow

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In JavaScript I want to get first date of the week and last date of the week by week number and year only.

For example if I my input is:

2(week),2012

Then my output should be:

2012-01-08 and 2012-01-14

In JavaScript I want to get first date of the week and last date of the week by week number and year only.

For example if I my input is:

2(week),2012

Then my output should be:

2012-01-08 and 2012-01-14

• javascript
• jquery

Share Improve this question Follow edited Oct 8, 2018 at 7:57 M.A.K. Ripon 2,14833 gold badges3030 silver badges4848 bronze badges asked Jan 10, 2012 at 12:18 balaphpbalaphp 1,32655 gold badges2020 silver badges4141 bronze badges 3

• How about if I give 2 for year 2013? What should it return? – James Jithin Commented Jan 10, 2012 at 12:27
• it should return the second week of the first date and last date.... – balaphp Commented Jan 10, 2012 at 12:29
• @balaphp actually it will return first and last date of 2nd week of the year 2013..m i right. ? – Chandresh M Commented Jan 10, 2012 at 12:32

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6 Answers 6

Sorted by: Reset to default 9

Try this:

var year = 2012;
var week = 2;
var d = new Date("Jan 01, " + year + " 01:00:00");
var w = d.getTime() + 604800000 * (week - 1);
var n1 = new Date(w);
var n2 = new Date(w + 518400000)

console.log(n1);
console.log(n2);

n1 contains the first day of the week
n2 contains the last day of the week

As for the constants:
604800000 is one week in milliseconds
518400000 is six days

A little change to @bardiir 's answer, if the first day of the year is not Sunday(or Monday) that result is not correct. You should minus the number of the first day.

Changed code

firstDay = new Date(2015, 0, 1).getDay();
console.log(firstDay);
var year = 2015;
var week = 67;
var d = new Date("Jan 01, " + year + " 01:00:00");
var w = d.getTime() - (3600000 * 24 * (firstDay - 1)) + 604800000 * (week - 1)
var n1 = new Date(w);
var n2 = new Date(w + 518400000)

console.log(n1.toString());
console.log(n2.toString());

if you wish the first is Sunday, change (firstDay-1) to firstDay

you can check and try with below link.

How to get first and last day of the week in JavaScript

It will may helpful to you.

Thanks.

Change previous answers and make it clear. @bardiir

// give the year and week
let year = 2021;
let week = 1;

// first date of year
let firstDateOfYear = new Date(year, 0, 1);
// get the day of first date in the year
let firstDayOfYear = firstDateOfYear.getDay();
console.log("first day of year", firstDayOfYear);

let timeofOneDay = 60 * 60 * 24 * 1000;
let timeofOneWeek = 60 * 60 * 24 * 7 * 1000;
// last day of the week, 6 days later
let timeof6Day = 60 * 60 * 24 * 6 * 1000;

// if week start from Monday
let timeOfFirstDay = firstDateOfYear.getTime() - (timeofOneDay * (firstDayOfYear - 1)) + timeofOneWeek * (week - 1);
let timeOfLastDay = timeOfFirstDay + timeof6Day;
console.log("week start from Monday");
console.log(new Date(timeOfFirstDay).toString());
console.log(new Date(timeOfLastDay).toString());

// if week from Sunday
timeOfFirstDay = firstDateOfYear.getTime() - (timeofOneDay * (firstDayOfYear - 0)) + timeofOneWeek * (week - 1);
timeOfLastDay = timeOfFirstDay + timeof6Day;
console.log("week start from Sunday");
console.log(new Date(timeOfFirstDay).toString());
console.log(new Date(timeOfLastDay).toString());

   dt = new Date();
   var firstDateOfWeek=(dt.setDate(dt.getDate()-dt.getDay()));
   var lastDateOfWeek=(dt.setDate(dt.getDate()+6-dt.getDay()));

The powerful way is for this issue, is to use moment.js

let date=new Date();
let start_date = moment(date).startOf('date').toDate()
let end_date = moment(date).endOf('date').toDate()

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