Grok all the things

grok (v): to understand (something) intuitively.

Timezones In Programming

🙄  Cynics & grumps

Truly the gift that keeps on giving, timezones. Or rather, the impossible reconciliation of timezones with the specificity and certainty required in computing. Let's dive headfirst into the headache-inducing world of coordinating dates and times across a mishmash of regions, daylight saving rules, and the ever-fragile sanity of developers everywhere.

The Earth is Round, Who Knew?

So, you might have heard that our planet is a spinning sphere hurtling through space. As it spins, different parts of the Earth are exposed to sunlight at different times. To make our puny human lives somewhat manageable, we have divided the Earth into 24 time zones generally based on longitudinal lines. Well done, humanity! Except, it's not that simple, is it? No, we had to go and invent political borders, daylight saving time (more on that later), and an array of other complications that can drive even the most stalwart programmer to the brink of despair.

Programming Languages and Time Zones

Most programming languages provide libraries or built-in functions for handling date and time operations. They attempt to ease the pain of dealing with time zones, but often result in developers Googling solutions in a frenzied panic at 3 am, only to uncover 50 different StackOverflow answers saying the same thing - "Just use this library!".

Here's a quick tour through how this madness unfolds in some popular programming languages:


Ah, Python, the snake that was supposed to make everything simple. Unfortunately, the built-in datetime module isn't timezone-aware by default. You can use the pytz library to add timezone support, though - just another item on your ever-growing list of third-party dependencies.

from datetime import datetime
import pytz

tz = pytz.timezone('America/New_York')
new_york_time =


JavaScript has a global Date object that you can use to wrestle with time zones. It will give you the local time by default but beware: daylight saving time can still throw you curveballs, and while you can extract the UTC time, there's no built-in support for handling other time zones. You can either hardcode offsets (please don't) or rely on a library like moment-timezone or the relatively modern luxon.

const now = new Date();
const utcTime = now.toISOString();
// Good luck handling other time zones!


Java boasts the java.time package (since Java 8) which includes the ZonedDateTime class for working with, you guessed it, date and time data in different time zones. As usual, it eases some of the pain but doesn't make it completely go away.

import java.time.ZonedDateTime;
import java.time.ZoneId;

ZoneId zone = ZoneId.of("America/New_York");
ZonedDateTime newYorkTime =;

Daylight Saving Time: Making Things Even Worse

Just when you think you've got a handle on time zones, daylight saving time (DST) comes along to ruin everything. For reasons that would make even Einstein question humanity's collective intellect, we have decided that certain regions should shift their clocks forward or backward by an hour during certain times of the year. This means that offset calculations need to account for these changes, lest your application cause international incidents by waking people up an hour early for their yoga class.

A Solution? The Time Lords' UTC

Coordinated Universal Time (UTC) is the agreed-upon standard time used by developers and systems worldwide. The idea is to store timestamps in UTC and convert them to local time only when they need to be displayed. This can be a lifesaver but requires constant vigilance to ensure you're always working in UTC, lest you introduce hard-to-find bugs that only surface when customers in a foreign land are trying to book a flight to Hawaii.


In the end, dealing with time zones is an exercise in patience, skill, and a healthy dose of self-loathing. Follow best practices, rely on libraries where it makes sense, and try not to pull your hair out. Remember to think of those brave developers who came before you, struggling with the same convoluted temporal quagmire, and know that you're not alone in your suffering. Happy coding! is a collection of articles on a variety of technology and programming articles assembled by James Padolsey. Enjoy! And please share! And if you feel like you can donate here so I can create more free content for you.