How to handle dates and times: a practical JS roundup
Jun 29, 2025 am 01:41 AMThe following points should be noted when processing dates and time in JavaScript: 1. When creating dates, use new Date() and prioritize ISO format to avoid browser differences; 2. When obtaining and setting date components, please note that getMonth() returns 0-11, which is inconsistent with 1-31 of getDate(); 3. When formatting, you can use padStart() or use date-fns and other libraries to improve flexibility; 4. For time zone processing, it is recommended to use Luxon, Moment-Timezone or Temporal API for more precise support. Mastering these core points can effectively deal with common problems.
Handling dates and times in JavaScript can be surprisedly tricky. Even though JS has a built-in Date
object, it's not always intuitive and comes with some gotchas. Here's a practical rundown of how to work with dates and times effectively in JavaScript.

Creating and Parsing Dates
The first thing you'll usually do is create a date. The most common way is using the new Date()
constructor. You can pass in various formats: no arguments (current time), a date string, or individual numbers for year, month, day, etc.

new Date(); // current date and time new Date('2025-04-05'); // April 5th, 2025 new Date(2025, 3, 5); // Note: months are zero-indexed! So 3 = April
One common pitfall: date strings can behave differently across browsers. For example, parsing '04/05/2025'
may return different results depending on the browser locale. To stay safe:
- Prefer ISO format (
YYYY-MM-DD
) when possible. - If you're constructing dates from user input or other sources, consider validating or normalizing them before creating a
Date
object.
Getting and Setting Date Components
Once you have a date object, you'll often want to extract or modify parts of it — like the day, month, or hour.

Use methods like:
-
.getDate()
/.setDate()
-
.getMonth()
/.setMonth()
(remember: 0 = January) -
.getFullYear()
/.setFullYear()
-
.getHours()
/.setHours()
, and so on for minutes, seconds, million seconds
If you need UTC versions, use .getUTCDate()
, .getUTCMonth()
, etc.
A small but easy-to-miss detail: getMonth()
returns 0–11, while getDate()
returns 1–31. That mismatch trips people up sometimes.
Formatting and Displaying Dates
JavaScript's native Date
methods for formatting aren't very flexible. You might see people using .toString()
, .toDateString()
, or .toLocaleDateString()
— but these given limited control over the output format and vary by browser.
For more control, here are a few options:
Use
.padStart()
to format numbers consistently:const month = String(date.getMonth() 1).padStart(2, '0');
Consider libraries like date-fns or Luxon if you need advanced formatting, localization, or relative time support.
- Use Luxon or Moment-Timezone.
- Or look into the newer Temporal API if you're working in environments that support it.
If your needs are simple, just building a formatted string manually with date components is totally fine.
Time Zones and Daylight Saving Changes
Time zones are one of the trickiest parts of working with dates. By default, JavaScript uses the system's local time zone. But if you need to handle specific zones or daylight saving changes, the built-in Date
object falls short.
You can get the timezone offset with .getTimezoneOffset()
, which returns minutes difference between UTC and local time. But that only tells you the offset at that specific moment — not the full IANA timezone name like "America/New_York".
For real timezone handling:
Otherwise, you may find yourself making assumptions that don't hold true everywhere.
That's basically all you need to know to get started with dates and times in JS. It's not rocket science, but there are enough edge cases to keep things interesting.
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