Convert a Timestamp to Relative Time (time ago) in JS

Convert a Timestamp to Relative Time (time ago) in JS #

To convert a timestamp to relative time:

1. Create an object using the Intl.RelativeTimeFormat() constructor.
2. Use the format() method on the constructor.
3. The format method formats the value according to the provided options.

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function relativeDays(timestamp) {
  const rtf = new Intl.RelativeTimeFormat('en', {
    numeric: 'auto',
  });
  const oneDayInMs = 1000 * 60 * 60 * 24;
  const daysDifference = Math.round(
    (timestamp - new Date().getTime()) / oneDayInMs,
  );

  return rtf.format(daysDifference, 'day');
}

// (Today is 22nd Jan, 2022

// 👇️ 7 days ago
console.log(relativeDays(new Date('2022-01-15').getTime()));

// 👇️ 2 days ago
console.log(relativeDays(new Date('2022-01-20').getTime()));

// 👇️ yesterday
console.log(relativeDays(new Date('2022-01-21').getTime()));

// 👇️ today
console.log(relativeDays(new Date().getTime()));

// 👇️ in 113 days
console.log(relativeDays(new Date('2022-05-15').getTime()));

The Intl.RelativeTimeFormat() constructor creates a Intl.RelativeTimeFormat object, on which we can call the format method.

The locale can be a string or array of BCP 27 language tag strings.

The second parameter is an options object.

The numeric property on the object has 2 possible values:

• always (default) - e.g. 1 day ago.
• auto - e.g. yesterday. The auto value allows to not always have to use numeric values in the output and looks more natural in certain cases.

The format method takes 2 parameters:

1. a value to use in the internationalized relative time message.
2. the unit to use in the message. Possible values are: year, quarter, month, week, day, hour, minute and second.

In the example, we passed day as the unit to the format method.

The getTime method returns the number of milliseconds elapsed between 1st of January, 1970 00:00:00 and the given date.

We subtracted the current timestamp from the passed in timestamp and converted the result from milliseconds to days.

The function returns a string, formatted as: 2 days ago, in 5 days, yesterday, etc.