I'm trying to get the same day of the year last week so i can compare some analytics.

Using moment i can easily do this

var today = new Date(); 
//Sunday 4 September 2016 - Week 36

var lastYear = new moment(today).subtract(12, 'months').toDate();
//Friday 4 September 2015 - Week 37

What i am trying to do is get the same 'Sunday' last year, so Sunday week 36 2015

Any idea how to do this?

I'm trying to get the same day of the year last week so i can compare some analytics.

Using moment i can easily do this

var today = new Date(); 
//Sunday 4 September 2016 - Week 36

var lastYear = new moment(today).subtract(12, 'months').toDate();
//Friday 4 September 2015 - Week 37

What i am trying to do is get the same 'Sunday' last year, so Sunday week 36 2015

Any idea how to do this?

• javascript
• date
• momentjs

3 Answers 3

Here's what I came up with:

let today    = moment();
let lastYear = moment().subtract(1, 'year')
                       .isoWeek(today.isoWeek())
                       .isoWeekday(today.isoWeekday());

It takes today as start point, subtracts a year, and sets the week and weekday to the ones from today.

So today (Tue Sept 13 2016, aka 2016-W37-2) last year was Tue Sept 8 2015 (aka 2015-W37-2).

As of version 2.0.0 moment.js supports .endOf('week') method, try

var lastYear = moment().subtract(1, 'years').endOf('week');

This will give you a 23:59:59 time, so you might also want to call .startOf('day') to get 00:00:00 of the same day:

var lastYear = moment().subtract(1, 'years').endOf('week').startOf('day');

Depending on your locale, your week may be from Monday to Sunday or from Sunday to Saturday, so I guess you'll have to account for that, too.

Edit

I've looked up documentation, and it appears you can set day of week this way, too:

moment().day(-7); // last Sunday (0 - 7)
moment().day(7); // next Sunday (0 + 7)
moment().day(10); // next Wednesday (3 + 7)
moment().day(24); // 3 Wednesdays from now (3 + 7 + 7 + 7)

So in your case it will be

var lastYear = moment().day(-52 * 7); // a Sunday 52 weeks ago

Or the two methods combined

var lastYear = moment().subtract(1, 'years').day(7); // a Sunday after the date that was 1 year ago

// Typescript

var lastYear: moment.Moment = moment().subtract(1, "year");