Working with Timezones in Day.js: A Node.js Developer’s Guide

Handling timezones in web applications can be a real headache for developers. As our applications become more global, dealing with different time zones efficiently becomes crucial. Today, let’s dive into how Day.js makes timezone handling a breeze in Node.js applications.

Understanding Timezone Basics in Day.js

Before we jump into the code, it’s important to note that Day.js doesn’t include timezone support out of the box. You’ll need to add the timezone plugin to get started. First, install Day.js and the timezone plugin:

npm install dayjs
npm install dayjs/plugin/timezone
npm install dayjs/plugin/utc

Let’s set up our basic configuration:

const dayjs = require('dayjs')
const utc = require('dayjs/plugin/utc')
const timezone = require('dayjs/plugin/timezone')

dayjs.extend(utc)
dayjs.extend(timezone)

Working with Different Timezones

One of the most common tasks is converting times between different zones. Here’s how you can do it:

// Create a time in one timezone
const tokyoTime = dayjs().tz('Asia/Tokyo')
console.log(`Time in Tokyo: ${tokyoTime.format('YYYY-MM-DD HH:mm:ss')}`)

// Convert to another timezone
const newYorkTime = tokyoTime.tz('America/New_York')
console.log(`Time in New York: ${newYorkTime.format('YYYY-MM-DD HH:mm:ss')}`)

Handling Daylight Saving Time (DST)

Day.js automatically handles DST transitions, which is super helpful. Here’s how you can check if a particular date is in DST:

const losAngeles = dayjs().tz('America/Los_Angeles')
const isDST = losAngeles.isDST()

Best Practices and Common Pitfalls

1. Always store dates in UTC format in your database
2. Convert to local timezone only when displaying to users
3. Be explicit about timezone conversions in your code
4. Remember to handle invalid timezone inputs gracefully

Here’s an example of implementing these practices:

// Store in UTC
const utcTime = dayjs.utc()

// Convert when displaying
function displayInUserTimezone(utcTimestamp, userTimezone) {
  try {
    return dayjs.utc(utcTimestamp).tz(userTimezone).format('YYYY-MM-DD HH:mm:ss')
  } catch (error) {
    console.error(`Invalid timezone: ${userTimezone}`)
    return dayjs.utc(utcTimestamp).format('YYYY-MM-DD HH:mm:ss Z') // Fallback to UTC
  }
}

Conclusion

Day.js makes timezone handling much more manageable in Node.js applications. By following these patterns and best practices, you can build robust applications that handle time-related operations reliably across different time zones.