Native Date vs. Moment.js
const utcDateString = '2024-01-22T15:30:00Z'; // 'Z' indicates UTC
const localDate = new Date(utcDateString);
console.log('Local Date:', localDate.toString());
This code will output the time in the user’s local time zone.
Moment.js and Time Zone processing
Unlike Native Date, to ensure that Moment.js interprets the time as UTC and then converts it to local time, the front-end developer can specify this explicitly.
const moment = require('moment');
const utcDateString = '2024-01-22T15:30:00Z';
const localTime = moment.utc(utcDateString).local();
console.log('Local Time with Moment.js:', localTime.format());
This code converts UTC time to the user’s local timezone using Moment.js.
Date and time format in API
Example of date-time format: “2024–01–22T15:30:00Z” (UTC time)
The format complies with the ISO 8601 standard.
The user sees the same time regardless of the time zone: Sometimes it is necessary for users, regardless of their location, to see the same time (for example, for global events, flight schedules, or timestamps in personal notebooks). In such cases, the API should return the time without specifying the time zone.
Example of date-time format: “2024–01–22T15:30:00”
Since a datetime string does not contain timezone information, the built-in Date object and JS libraries such as Moment.js, Luxon, and Day.js assume the user’s local timezone. So the output will be the same as the input datetime, but interpreted as local time.
However, if the client-side front-end developer interprets this format as UTC time, as shown in the example at the beginning of the article, the user will see an unexpectedly converted date and time.
NOTE: If your API returns a time with a timezone specified, both the built-in Date object and Moment.js will convert it.
Example of a datetime format: “2024–01–22T15:30:00–05:00” (time in a specific time zone, such as EST)
An example of what a user would see in GMT+4: “2024-01-23 00:30:00”
It is important for the backend developer to clearly document the date and time format used in your API objects.
It is important for the frontend developer to check the date and time format returned by the API.
It is important for both:
Test your application in different time zones to ensure consistency.