The Best JavaScript Date Time Library

I am using momentjs before, and the library works really well. But After knowing Day.js · 2kB JavaScript date utility library, I have been using it for most of my projects, because I really like it small cause we don't like to have large JS files being included in our website that would affect the performance. I believe that a large library has an impact on our website, especially when loading it for the first time.

You can use `daysjs` in a node project by installing it using npm/yarn.

// npm
npm install dayjs

// yarn
yarn add dayjs

or You can use CDN

<!-- CDN example (jsDelivr) -->
<script src="https://cdn.jsdelivr.net/npm/dayjs@1/dayjs.min.js"></script>
<script>dayjs().format()</script>

For more on how to use it on your project, you can check it here Installation · Day.js.

Here are the things why I love dayjs

1. It has a ton of display options, you can display your date and time in a format you like.

   dayjs().format() 
   // current date in ISO8601, without fraction seconds e.g. '2020-04-02T08:02:17-05:00'
   
   dayjs('2019-01-25').format('[YYYYescape] YYYY-MM-DDTHH:mm:ssZ[Z]') 
   // 'YYYYescape 2019-01-25T00:00:00-02:00Z'
   
   dayjs('2019-01-25').format('DD/MM/YYYY') // '25/01/2019'

2. Plugins: I like other functionality to be in a plugin that way, I can only grab something I need before using it. Like for example the UTC plugin. I really need this because if you're working on data that is being saved on the database. You want it to be in UTC format that way it's a lot easier to show time in different time zones.

   var utc = require('dayjs/plugin/utc')
   dayjs.extend(utc)
   
   // default local time
   dayjs().format() //2019-03-06T17:11:55+08:00
   
   // UTC mode
   dayjs.utc().format() // 2019-03-06T09:11:55Z
   
   // convert local time to UTC time
   dayjs().utc().format() // 2019-03-06T09:11:55Z 
   
   // While in UTC mode, all display methods will display in UTC time instead of local time.
   // And all getters and setters will internally use the Date#getUTC* and Date#setUTC* methods instead of the Date#get* and Date#set* methods.
   dayjs.utc().isUTC() // true
   dayjs.utc().local().format() //2019-03-06T17:11:55+08:00
   dayjs.utc('2018-01-01', 'YYYY-MM-DD') // with CustomParseFormat plugin

3. Manipulation: you can easily manipulate dates like adding 1 day to a date or minus 1 day to a date etc.

   dayjs('2019-01-25').add(1, 'day').subtract(1, 'year').year(2009).toString()

4. Query: you can do some conditional that way you can check the date your trying to evaluate.

   // example
   // This requires the IsBetween plugin to work
   var isBetween = require('dayjs/plugin/isBetween')
   dayjs.extend(isBetween)
   
   dayjs.extend(isBetween)
   dayjs('2010-10-20').isBetween('2010-10-19', dayjs('2010-10-25')) 
   // default milliseconds

5. Duration: This is a really important functionality because you can easily calculate the duration of a date to the current date.

   dayjs.extend(duration)
   dayjs.extend(relativeTime)
   dayjs.duration(1, "minutes").humanize(); // a minute
   dayjs.duration(2, "minutes").humanize(); // 2 minutes
   dayjs.duration(24, "hours").humanize();  // a day

6. Time zone: You can easily set time zones.

   dayjs.extend(utc)
   dayjs.extend(timezone)
   
   // current time zone is 'Europe/Berlin' (offset +01:00)
   // Parsing
   dayjs.tz("2013-11-18 11:55:20", "America/Toronto") // '2013-11-18T11:55:20-05:00'
   
   // Converting (from time zone 'Europe/Berlin'!)
   dayjs("2013-11-18 11:55:20").tz("America/Toronto") // '2013-11-18T05:55:20-05:00'