Well it's pretty easy if you aren't overly concerned with accuracy. What wrong with the trivial method?

function timeDifference(current, previous) {


var msPerMinute = 60 * 1000;
var msPerHour = msPerMinute * 60;
var msPerDay = msPerHour * 24;
var msPerMonth = msPerDay * 30;
var msPerYear = msPerDay * 365;


var elapsed = current - previous;


if (elapsed < msPerMinute) {
return Math.round(elapsed/1000) + ' seconds ago';
}


else if (elapsed < msPerHour) {
return Math.round(elapsed/msPerMinute) + ' minutes ago';
}


else if (elapsed < msPerDay ) {
return Math.round(elapsed/msPerHour ) + ' hours ago';
}


else if (elapsed < msPerMonth) {
return 'approximately ' + Math.round(elapsed/msPerDay) + ' days ago';
}


else if (elapsed < msPerYear) {
return 'approximately ' + Math.round(elapsed/msPerMonth) + ' months ago';
}


else {
return 'approximately ' + Math.round(elapsed/msPerYear ) + ' years ago';
}
}

Working example here.

You might want to tweak it to handle the singular values better (e.g. 1 day instead of 1 days) if that bothers you.

Here is the exact mimic of twitter time ago without plugins:

function timeSince(timeStamp) {
var now = new Date(),
secondsPast = (now.getTime() - timeStamp) / 1000;
if (secondsPast < 60) {
return parseInt(secondsPast) + 's';
}
if (secondsPast < 3600) {
return parseInt(secondsPast / 60) + 'm';
}
if (secondsPast <= 86400) {
return parseInt(secondsPast / 3600) + 'h';
}
if (secondsPast > 86400) {
day = timeStamp.getDate();
month = timeStamp.toDateString().match(/ [a-zA-Z]*/)[0].replace(" ", "");
year = timeStamp.getFullYear() == now.getFullYear() ? "" : " " + timeStamp.getFullYear();
return day + " " + month + year;
}
}


const currentTimeStamp = new Date().getTime();


console.log(timeSince(currentTimeStamp));

Gist https://gist.github.com/timuric/11386129

Fiddle http://jsfiddle.net/qE8Lu/1/

Hope it helps.

For anyone interested, I ended up creating a Handlebars helper to do this. Usage:

    \{\{#beautify_date}}
\{\{timestamp_ms}}
\{\{/beautify_date}}

Helper:

    Handlebars.registerHelper('beautify_date', function(options) {
var timeAgo = new Date(parseInt(options.fn(this)));


if (Object.prototype.toString.call(timeAgo) === "[object Date]") {
if (isNaN(timeAgo.getTime())) {
return 'Not Valid';
} else {
var seconds = Math.floor((new Date() - timeAgo) / 1000),
intervals = [
Math.floor(seconds / 31536000),
Math.floor(seconds / 2592000),
Math.floor(seconds / 86400),
Math.floor(seconds / 3600),
Math.floor(seconds / 60)
],
times = [
'year',
'month',
'day',
'hour',
'minute'
];


var key;
for(key in intervals) {
if (intervals[key] > 1)
return intervals[key] + ' ' + times[key] + 's ago';
else if (intervals[key] === 1)
return intervals[key] + ' ' + times[key] + ' ago';
}


return Math.floor(seconds) + ' seconds ago';
}
} else {
return 'Not Valid';
}
});

Inspirated on Diego Castillo awnser's and in the timeago.js plugin, I wrote my own vanilla plugin for this.

var timeElement = document.querySelector('time'),
time = new Date(timeElement.getAttribute('datetime'));


timeElement.innerText = TimeAgo.inWords(time.getTime());

var TimeAgo = (function() {
var self = {};
  

// Public Methods
self.locales = {
prefix: '',
sufix:  'ago',
    

seconds: 'less than a minute',
minute:  'about a minute',
minutes: '%d minutes',
hour:    'about an hour',
hours:   'about %d hours',
day:     'a day',
days:    '%d days',
month:   'about a month',
months:  '%d months',
year:    'about a year',
years:   '%d years'
};
  

self.inWords = function(timeAgo) {
var seconds = Math.floor((new Date() - parseInt(timeAgo)) / 1000),
separator = this.locales.separator || ' ',
words = this.locales.prefix + separator,
interval = 0,
intervals = {
year:   seconds / 31536000,
month:  seconds / 2592000,
day:    seconds / 86400,
hour:   seconds / 3600,
minute: seconds / 60
};
    

var distance = this.locales.seconds;
    

for (var key in intervals) {
interval = Math.floor(intervals[key]);
      

if (interval > 1) {
distance = this.locales[key + 's'];
break;
} else if (interval === 1) {
distance = this.locales[key];
break;
}
}
    

distance = distance.replace(/%d/i, interval);
words += distance + separator + this.locales.sufix;


return words.trim();
};
  

return self;
}());




// USAGE
var timeElement = document.querySelector('time'),
time = new Date(timeElement.getAttribute('datetime'));


timeElement.innerText = TimeAgo.inWords(time.getTime());

<time datetime="2016-06-13"></time>

Datetime plugins exist because it's very hard to get it right. This video explaining date-time inconsistencies will shed some light on the issue.

All above solutions without plugins are incorrect.

For working with Dates and times using a plugin is preferable. Out of the hundreds of plugins that deal with it, we use Moment.js and it's doing the job.

From the twitter API dcumentation we can see their timestamp format:

"created_at":"Wed Aug 27 13:08:45 +0000 2008"

We can parse with it with Moment.js

const postDatetime = moment(
"Wed Aug 27 13:08:45 +0000 2008",
"dddd, MMMM Do, h:mm:ss a, YYYY"
);
const now = moment();
const timeAgo = now.diff(postDatetime, 'seconds');

To specify the preferred time unit for the diff, we can use the isSame method. eg:

if (now.isSame(postDatetime, 'day')) {
const timeUnit = 'days';
}

Overall, constructing something like:

`Posted ${timeAgo} ${timeUnit} ago`;

Refer to your plugin's documentation for handling relative time (ie: "How long ago?") calculations.

You can use machinepack-datetime for this purpose. It is easy and clear with its defined API.

tutorialSchema.virtual('createdOn').get(function () {
const DateTime = require('machinepack-datetime');
let timeAgoString = "";
try {
timeAgoString = DateTime.timeFrom({
toWhen: DateTime.parse({
datetime: this.createdAt
}).execSync(),
fromWhen: new Date().getTime()
}).execSync();
} catch(err) {
console.log('error getting createdon', err);
}
return timeAgoString; // a second ago
});

If you need multilingual and don't want to add a big library like moment. intl-relativeformat from yahoo it a nice solution.

var rf = new IntlRelativeFormat('en-US');


var posts = [
{
id   : 1,
title: 'Some Blog Post',
date : new Date(1426271670524)
},
{
id   : 2,
title: 'Another Blog Post',
date : new Date(1426278870524)
}
];


posts.forEach(function (post) {
console.log(rf.format(post.date));
});
// => "3 hours ago"
// => "1 hour ago"

Update April 4, 2021:

I've converted the below code to a node package. Here's the repository.

Intl.RelativeTimeFormat - Native API

[✔] (Dec' 18) a Stage 3 proposal, and already implemented in Chrome 71
[✔] (Oct' 20) at Stage 4 (finished), and ready for inclusion in the formal ECMAScript standard

// in miliseconds
var units = {
year  : 24 * 60 * 60 * 1000 * 365,
month : 24 * 60 * 60 * 1000 * 365/12,
day   : 24 * 60 * 60 * 1000,
hour  : 60 * 60 * 1000,
minute: 60 * 1000,
second: 1000
}


var rtf = new Intl.RelativeTimeFormat('en', { numeric: 'auto' })


var getRelativeTime = (d1, d2 = new Date()) => {
var elapsed = d1 - d2


// "Math.abs" accounts for both "past" & "future" scenarios
for (var u in units)
if (Math.abs(elapsed) > units[u] || u == 'second')
return rtf.format(Math.round(elapsed/units[u]), u)
}


// test-list of dates to compare with current date
[
'10/20/1984',
'10/20/2015',
+new Date() - units.year,
+new Date() - units.month,
+new Date() - units.day,
+new Date() - units.hour,
+new Date() - units.minute,
+new Date() + units.minute*2,
+new Date() + units.day*7,
]
.forEach(d => console.log(
new Date(d).toLocaleDateString(),
new Date(d).toLocaleTimeString(),
'(Relative to now) →',
getRelativeTime(+new Date(d))
))

Intl.RelativeTimeFormat is available by default in V8 v7.1.179 and Chrome 71. As this API becomes more widely available, you’ll find libraries such as Moment.js, Globalize, and date-fns dropping their dependency on hardcoded CLDR databases in favor of the native relative time formatting functionality, thereby improving load-time performance, parse- and compile-time performance, run-time performance, and memory usage.

MomentJS Answer

For Moment.js users, it has fromNow() function that returns "x days" or "x hours ago" from current date/time.

moment([2007, 0, 29]).fromNow();     // 4 years ago
moment([2007, 0, 29]).fromNow(true); // 4 years

const units = [
['year', 31536000000],
['month', 2628000000],
['day', 86400000],
['hour', 3600000],
['minute', 60000],
['second', 1000],
]


const rtf = new Intl.RelativeTimeFormat('en', { style:'narrow'})
const relatime = elapsed => {
for (const [unit, amount] of units) {
if (Math.abs(elapsed) > amount || unit === 'second') {
return rtf.format(Math.round(elapsed/amount), unit)
}
}
}

had some fun golfing it 192b hehe

const relatime = e=>{for(let[u,a]of Object.entries({year:31536e6,month:2628e6,day:864e5,hour:36e5,minute:6e4,second:1e3})){if(Math.abs(e)>a||a===1e3){return new Intl.RelativeTimeFormat('en',{style:'narrow'}).format(~~(e/a),u)}}}

I also tested a functionnal version while golfing:

const rtf = new Intl.RelativeTimeFormat('en', { style:'narrow'})
const relatime = Object.entries({year:31536e6,month:2628e6,day:864e5,hour:36e5,minute:6e4,second:1e3})
.reduce((f, [unit, amount]) => amount === 1e3
? f(elapsed => rtf.format(Math.round(elapsed/amount), unit))
: next => f(e => Math.abs(e) < amount
? next(elapsed)
: rtf.format(Math.round(elapsed/amount), unit)), _=>_)

All right i really have to get back to work now...

Typescript and Intl.RelativeTimeFormat (2020)

Combined Typescript implementation of @vsync and @kigiri approach using Web API RelativeTimeFormat.

const units: {unit: Intl.RelativeTimeFormatUnit; ms: number}[] = [
{unit: "year", ms: 31536000000},
{unit: "month", ms: 2628000000},
{unit: "day", ms: 86400000},
{unit: "hour", ms: 3600000},
{unit: "minute", ms: 60000},
{unit: "second", ms: 1000},
];
const rtf = new Intl.RelativeTimeFormat("en", {numeric: "auto"});


/**
* Get language-sensitive relative time message from Dates.
* @param relative  - the relative dateTime, generally is in the past or future
* @param pivot     - the dateTime of reference, generally is the current time
*/
export function relativeTimeFromDates(relative: Date | null, pivot: Date = new Date()): string {
if (!relative) return "";
const elapsed = relative.getTime() - pivot.getTime();
return relativeTimeFromElapsed(elapsed);
}


/**
* Get language-sensitive relative time message from elapsed time.
* @param elapsed   - the elapsed time in milliseconds
*/
export function relativeTimeFromElapsed(elapsed: number): string {
for (const {unit, ms} of units) {
if (Math.abs(elapsed) >= ms || unit === "second") {
return rtf.format(Math.round(elapsed / ms), unit);
}
}
return "";
}

(2021) If you only need days, like 243 days ago or in 127 days, then it can be super simple:

function relativeDays(timestamp) {
const rtf = new Intl.RelativeTimeFormat('en', { numeric: 'auto' });
const aDay = 1000 * 60 * 60 * 24;
const diffInDays = Math.round((timestamp - Date.now()) / aDay);
return rtf.format(diffInDays, 'day');
}

Try running the snippet below:

function relativeDays(timestamp) {
const rtf = new Intl.RelativeTimeFormat('en', { numeric: 'auto' });
const aDay = 1000 * 60 * 60 * 24;
const diffInDays = Math.round((timestamp - Date.now()) / aDay);
return rtf.format(diffInDays, 'day');
}


console.log(relativeDays(Date.now() - 86400000)); // "yesterday"
console.log(relativeDays(Date.now())); // "today"
console.log(relativeDays(Date.now() + 86400000)); // "tomorrow"
console.log(relativeDays(Date.now() - 8640000000)); // "100 days ago"
console.log(relativeDays(Date.now() + 8640000000)); // "in 100 days"


// Note my timestamp argument is a number in ms, if you want to pass in a Date object, modify the function accordingly

Adding my code for time labels based on the current design from twitter

function timeElapsed(targetTimestamp:string) {
let currentDate=new Date();
let currentTimeInms = currentDate.getTime();
let targetDate=new Date(targetTimestamp);
let targetTimeInms = targetDate.getTime();
let elapsed = Math.floor((currentTimeInms-targetTimeInms)/1000);
if(elapsed<1) {
return '0s';
}
if(elapsed<60) { //< 60 sec
return `${elapsed}s`;
}
if (elapsed < 3600) { //< 60 minutes
return `${Math.floor(elapsed/(60))}m`;
}
if (elapsed < 86400) { //< 24 hours
return `${Math.floor(elapsed/(3600))}h`;
}
if (elapsed < 604800) { //<7 days
return `${Math.floor(elapsed/(86400))}d`;
}
if (elapsed < 2628000) { //<1 month
return `${targetDate.getDate()} ${MonthNames[targetDate.getMonth()]}`;
}
return `${targetDate.getDate()} ${MonthNames[targetDate.getMonth()]} ${targetDate.getFullYear()}`; //more than a monh
}

Like the OP, I tend to avoid plugins and packages for code that seems trivial to write myself. Of course, then I end up writing my own packages.

I created this NPM package so I could easily convert any date to a relative time string (e.g., "yesterday", "last week", "2 years ago"), with translations for internationalization (i18n) and localization (l10n).

Feel free to look through the source code; it is a pretty small, single file. Most of what's in the repository is for unit tests, version control, and publishing to NPM.

export default class RTF {
formatters;
options;


/**
* @param options \{\{localeMatcher: string?, numeric: string?, style: string?}} Intl.RelativeTimeFormat() options
*/
constructor(options = RTF.defaultOptions) {
this.options = options;
this.formatters = { auto: new Intl.RelativeTimeFormat(undefined, this.options) };
}


/**
* Add a formatter for a given locale.
*
* @param locale {string} A string with a BCP 47 language tag, or an array of such strings
* @returns {boolean} True if locale is supported; otherwise false
*/
addLocale(locale) {
if (!Intl.RelativeTimeFormat.supportedLocalesOf(locale).includes(locale)) {
return false;
}
if (!this.formatters.hasOwnProperty(locale)) {
this.formatters[locale] = new Intl.RelativeTimeFormat(locale, this.options);
}
return true;
}


/**
* Format a given date as a relative time string, with support for i18n.
*
* @param date {Date|number|string} Date object (or timestamp, or valid string representation of a date) to format
* @param locale {string?} i18n code to use (e.g. 'en', 'fr', 'zh'); if omitted, default locale of runtime is used
* @returns {string} Localized relative time string (e.g. '1 minute ago', '12 hours ago', '3 days ago')
*/
format(date, locale = "auto") {
if (!(date instanceof Date)) {
date = new Date(Number.isNaN(date) ? Date.parse(date) : date);
}
if (!this.formatters.hasOwnProperty(locale) && !this.addLocale(locale)) {
locale = "auto";
}


const elapsed = date - Date.now();


for (let i = 0; i < RTF.units.length; i++) {
const { unit, value } = RTF.units[i];
if (unit === 'second' || Math.abs(elapsed) >= value) {
return this.formatters[locale].format(Math.round(elapsed/value), unit);
}
}
}


/**
* Generate HTTP middleware that works with popular frameworks and i18n tools like Express and i18next.
*
* @param rtf {RTF?} Instance of RTF to use; defaults to a new instance with default options
* @param reqProp {string?} Property name to add to the HTTP request context; defaults to `rtf`
* @param langProp {string?} Property of HTTP request context where language is stored; defaults to `language`
* @returns {function(*, *, *): *} HTTP middleware function
*/
static httpMiddleware(rtf = new RTF(), reqProp = "rtf", langProp = "language") {
return (req, res, next) => {
req[reqProp] = (date) => rtf.format(date, req[langProp]);
next();
};
}


/**
* Default options object used by Intl.RelativeTimeFormat() constructor.
*
* @type \{\{localeMatcher: string, numeric: string, style: string}}
*/
static defaultOptions = {
localeMatcher: "best fit",
numeric: "auto", // this intentionally differs from Intl.RelativeTimeFormat(), because "always" is dumb
style: "long",
};


/**
* Used to determine the arguments to pass to Intl.RelativeTimeFormat.prototype.format().
*/
static units = [
{ unit: "year", value: 365 * 24 * 60 * 60 * 1000 },
{ unit: "month", value: 365 / 12 * 24 * 60 * 60 * 1000 },
{ unit: "week", value: 7 * 24 * 60 * 60 * 1000 },
{ unit: "day", value: 24 * 60 * 60 * 1000 },
{ unit: "hour", value: 60 * 60 * 1000 },
{ unit: "minute", value: 60 * 1000 },
{ unit: "second", value: 1000 },
];


/**
* Enumerated values for options object used by Intl.RelativeTimeFormat() constructor.
*
* @type \{\{localeMatcher: {lookup: string, default: string, bestFit: string}, numeric: {always: string, default: string, auto: string}, style: {default: string, short: string, narrow: string, long: string}}}
*/
static opt = {
localeMatcher: {
bestFit: "best fit",
lookup: "lookup",
},
numeric: {
always: "always",
auto: "auto",
},
style: {
long: "long",
narrow: "narrow",
short: "short",
},
};
}

Key Features

• Uses native JavaScript Intl.RelativeTimeFormat under the hood, with no dependencies.
• Formats any Date object, timestamp, or valid string representation of a date that can be parsed by Date.parse().
• Provides HTTP middleware compatible with popular REST frameworks like Express and i18n tools like i18next.

Why use this instead of Intl.RelativeTimeFormat.prototype.format()?

Intl.RelativeTimeFormat.prototype.format() takes two arguments: value and units.

const rtf = new Intl.RelativeTimeFormat("en", { style: "narrow" });


expect(rtf.format(-1, "day")).toBe("1 day ago");
expect(rtf.format(10, "seconds")).toBe("in 10 sec.");

In order to convert a Date object, timestamp, or date string, you need to write a bunch of boilerplate. This library saves you that headache, and can also be used to generate a middleware function for your REST API that works with your i18n library.

if you are using PHP time(), you can try this instead;

function time_stamp(session_time)
{
var time_difference ="<?php echo time() ?>" - session_time;
var seconds = time_difference;
var minutes = Math.round(time_difference / 60);
var hours = Math.round(time_difference / 3600);
var days = Math.round(time_difference / 86400);
var weeks = Math.round(time_difference / 604800);
var months = Math.round(time_difference / 2419200);
var years = Math.round(time_difference / 29030400);


if (seconds <= 60) {
return seconds+" Secs Ago";
} else if (minutes <= 60) {
if (minutes == 1) {
return "1 Min Ago";
} else {
return minutes+" Mins Ago";
}
} else if (hours <= 24) {
if (hours == 1) {
return "1 Hour Ago";
} else {
return hours+" Hours Ago";
}
} else if (days <= 7) {
if (days == 1) {
return "1 Day Ago";
} else {
return days+" Days Ago";
}
} else if (weeks <= 4) {
if (weeks == 1) {
return "1 Week Ago";
} else {
return weeks+" Weeks Ago";
}
} else if (months <= 12) {
if (months == 1) {
return "1 Month Ago";
} else {
return months+" Months Ago";
}
} else {
if (years == 1) {
return "1 Year Ago";
} else {
return years+" Years Ago";
}
}
}

to use this, just LITERALLY COPY ALL of this code & just import it in your component or where ever & just place in your ISOstring() date inside: showTimeAgo("2022-06-20T13:42:29-05:00") & you will get automatic time updates for every scenario.

sidenote: I made an npm package for this https://www.npmjs.com/package/showtimeago

export const showTimeAgo = () => {
const MONTH_NAMES = [
'January',
'February',
'March',
'April',
'May',
'June',
'July',
'August',
'September',
'October',
'November',
'December',
];


function getOrdinalNum() {
return (
n +
(n > 0
? ['th', 'st', 'nd', 'rd'][
(n > 3 && n < 21) || n % 10 > 3 ? 0 : n % 10
]
: '')
);
}


function getFormattedDate(
date,
preformattedDate = false,
hideYear = false
) {
const day = date.getDate();
const month = MONTH_NAMES[date.getMonth()];
const year = date.getFullYear();
let hours = date.getHours();
let minutes = date.getMinutes();


let ampm = hours >= 12 ? 'pm' : 'am';


switch(true){
case (hours > 12):
hours = hours - 12;
break;
case (hours === 0):
hours = 12;
break;
case(minutes < 10):
minutes = `0${minutes}`;
break;
case(preformattedDate):
// Today at 10:20am
// Yesterday at 10:20am
return `${preformattedDate} at ${hours}:${minutes} ${ampm}`;


case(hideYear):
// January 10th at 10:20pm
return `${month} ${getOrdinalNum(
day
)}, at ${hours}:${minutes} ${ampm}`;
default:
// January 10th 2022 at 10:20pm
return `${month} ${getOrdinalNum(
day
)}, ${year} at ${hours}:${minutes} ${ampm}`;
}
        

}


// --- Main function
function timeAgo(dateParam) {
if (!dateParam) {
return null;
}


const date =
typeof dateParam === 'object' ? dateParam : new Date(dateParam);
const DAY_IN_MS = 86400000; // 24 * 60 * 60 * 1000
const today = new Date();


const yesterday = new Date(today - DAY_IN_MS);


const seconds = Math.round((today - date) / 1000);
const minutes = Math.round(seconds / 60);
const hour = Math.round(seconds / 3600);
const day = Math.round(seconds / 86400);
const month = Math.round(seconds / 2629800);
const year = Math.floor(seconds / 31536000);
const isToday = today.toDateString() === date.toDateString();
const isYesterday =
yesterday.toDateString() === date.toDateString();
const isThisYear = today.getFullYear() === date.getFullYear();


switch(true){
case (seconds < 5):
return 'now';
case (seconds < 60):
return `${seconds} seconds ago`;
case (seconds < 90):
return 'about a minute ago';
case (minutes < 60):
return `${minutes} minutes ago`;
case (hour === 1 && hour < 2):
return `${hour} hour ago`; // 1 hour ago
case (hour > 1 && hour <= 12):
return `${hour} hours ago`; // 2 hours ago
case (isToday):
return getFormattedDate(date, 'Today'); // Today at 10:20am
case (isYesterday):
return getFormattedDate(date, 'Yesterday'); // Yesterday at 10:20am
case(day > 1 && day <= 30):
return `${day} days ago`; // 2 days ago
case (isThisYear):
return getFormattedDate(date, false, true); // January 10th at 10:20pm
case (day > 30 && month <= 1):
return `${hour} month ago`; // 1 month ago
case (month > 1 && month <= 12):
return `${month} months ago`; // 2 months ago
case (year === 1):
return `${year} year ago`; // 1 year ago
case (year > 1):
return `${year} years ago`; // 2 years ago
default:
return getFormattedDate(date); // January 10th 2022 at 10:20pm
}
}


return timeAgo(date);
};


console.log(showTimeAgo("2022-06-20T13:42:29-05:00"));-05:00"))