Choosing the Right Time Library for Your JS Project: A Comparison of Moment.js, Luxon, and Day.js

In the world of development, handling date and time correctly is crucial for building robust and reliable applications. Whether you’re dealing with scheduling events, showing time-sensitive data, or handling time zone conversions, picking the right time library can save you a lot of headaches. While JavaScript’s native Date object provides basic functionality, many developers turn to external libraries for more complex date handling. Some of the most popular libraries in this space are Moment.js, Luxon, and Day.js. Each of these libraries has its own history, feature set, and suitability for different types of projects

In this article, I will compare Moment.js, Luxon, and Day.js based on their history, functions, performance, and the types of projects they are best suited for.

Moment.js: The Old Guard Moment.js, created in 2011 by Tim Wood, became the most popular JavaScript library for date and time handling. It was praised for its simplicity and extensive feature set. However, it had limitations, including a large size (around 300 KB), lack of full time zone support, and issues with immutability. Due to these shortcomings, Moment.js is now in maintenance mode, with no major updates, and developers are encouraged to explore alternatives.

Luxon: A Modern Solution for Time Zones Luxon, created by Isaac Cambron who was a developer in Moment team in 2017, was designed to address Moment.js’s limitations. Built on the Intl API and IANA Time Zone Database, Luxon offers powerful time zone handling, daylight saving time (DST) adjustments, and locale-based formatting. It’s a smaller, more modern library, ideal for applications needing accurate time zone support.

Day.js: A Lightweight Alternative Day.js, created in 2018, is a lightweight alternative to Moment.js, with a size of just 2 KB. It is mostly API-compatible with Moment.js but offers a leaner and faster experience. While it doesn’t have Luxon’s advanced time zone handling, Day.js can extend its functionality via plugins for basic date manipulation and UTC conversions.

so let’s compare some of their basic functionalities.

so in below examples you may notice that the moment and Day.js share a very similar api.

moment(); // Returns current date and time (moment)
DateTime.local(); // Returns current date and time (luxon)
dayjs(); // Returns current date and time (day.js)

moment().format("YYYY-MM-DD HH:mm:ss"); // Custom format  (moment)
DateTime.local().toFormat("yyyy-MM-dd HH:mm:ss"); // Custom format (luxon)
dayjs().format("YYYY-MM-DD HH:mm:ss"); // Custom format (day.js)

moment("2022-01-01", "YYYY-MM-DD"); // Parse specific date (moment)
DateTime.fromFormat("2022-01-01", "yyyy-MM-dd"); // Parse specific date (luxon)
dayjs("2022-01-01", "YYYY-MM-DD"); // Parse specific date (day.js)

moment.tz("2022-01-01 12:00", "America/New_York"); // Convert to a specific time zone (moment)

DateTime.fromISO("2022-01-01T12:00:00", { zone: "America/New_York" }); // Convert to a specific time zone (luxon)

dayjs.tz("2022-01-01 12:00", "America/New_York"); // Convert to a specific time zone (day.js)        

While Moment.js and Day.js require additional plugins for handling time zones, Luxon has built-in support for time zone handling using the IANA Time Zone Database.( explained below what is IANA) . This makes Luxon a more convenient choice for handling complex time zone conversions.

What is IANA DB ??

The IANA Time Zone Database, maintained by the Internet Assigned Numbers Authority (IANA), provides comprehensive and up-to-date time zone information worldwide. It includes time zone offsets from UTC, rules for Daylight Saving Time (DST), and historical time zone transitions. This database is crucial for accurate time zone conversions, ensuring that applications account for shifts in time due to DST changes and other regional adjustments.

• Luxon natively uses the IANA Time Zone Database for time zone and DST management. (What is DST ?? explained below)
• Moment.js and Day.js can use IANA data, but they need the appropriate plugins (Moment Timezone and Day.js Timezone) to access it.

What is DST ??

Daylight Saving Time (DST) is the practice of moving the clocks forward by one hour during the warmer months (typically spring and summer) to make better use of daylight in the evenings. The idea is to extend daylight hours in the evening, reducing the need for artificial lighting and thereby saving energy. In the fall, clocks are set back by one hour to standard time.

DST is not observed universally, and the start and end dates vary by country and region. This shift can sometimes lead to confusion, especially when dealing with time-sensitive applications across different time zones. Modern libraries like Luxon, Moment.js, and Day.js help manage DST transitions by adjusting for these changes automatically, ensuring that applications accurately reflect local times regardless of time zone differences.

Handling DST with Moment Luxon and Day.js :

Luxon: It offers advanced DST handling by leveraging the IANA Time Zone Database. It automatically detects and adjusts for DST transitions, handles non-existent and ambiguous times, and provides built-in functions like isInDST to check if a time falls in DST. It is robust for both current and historical time zone and DST management.

Moment.js (with Moment-Timezone): Moment.js also supports DST transitions when using the Moment-Timezone plugin, but its handling is not as automatic or comprehensive as Luxon. It requires manual configuration to work with DST and may not offer the same level of support for historical changes or edge cases like non-existent or ambiguous times.

Day.js: While Day.js can handle DST if you add the timezone plugin, it has more limited functionality compared to Luxon. For example, it does not automatically handle DST in the same way and requires more manual intervention when working with time zone conversions and DST.

Which Library Should You Use?

• Moment.js: Best for legacy projects or situations where you already have extensive use of Moment.js in your codebase. While it’s still widely used, it’s in maintenance mode, so it’s not recommended for new projects.
• Luxon: Best for modern applications that require time zone handling, DST adjustments, and localization. If you need to work with multiple time zones or perform accurate date/time calculations, Luxon is the ideal choice. It’s highly recommended for international apps, financial applications, and event scheduling systems.
• Day.js: Best for lightweight applications or projects where performance and small file size are critical. Day.js is perfect when you need a fast, minimal library that offers similar functionality to Moment.js but with a smaller footprint. It’s ideal for projects where date manipulation is relatively simple, and advanced features like extreame time zone handling are not much required. (Day.js can handle time zone operations, but it does not offer the same level of advanced DST handling or automatic adjustments as Luxon, so it’s more appropriate for applications that do not require extensive time zone management.)