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Everything About Time Zones
Articles covering the basics, clock changes, scheduling across time zones, and the technical details behind how computers handle time.
What Is a Time Zone?
A clear explanation of what time zones are, why they exist, and how the world's 38 zones work in practice.
The BasicsWhat Is UTC?
UTC — Coordinated Universal Time — is the world's primary time standard. Here's what it is, how it works, and why software uses it everywhere.
The BasicsWhat Is GMT?
GMT — Greenwich Mean Time — is the historical predecessor to UTC. Learn what it means, where it's used, and how it differs from UTC today.
The BasicsWhat Is an IANA Time Zone?
IANA time zone names like 'America/New_York' are the global standard for identifying time zones in software. Here's why they exist and how to read them.
The BasicsWhat Does UTC Offset Mean?
UTC offsets like UTC+5:30 or UTC−8 tell you how far ahead or behind a location is from the world's time standard. Here's how to read and use them.
The BasicsWhat Is the International Date Line?
The International Date Line is where one calendar day ends and another begins. Here's where it is, why it zig-zags, and what happens when you cross it.
The BasicsHow Many Time Zones Are There?
The answer is more complex than you'd think — Earth has 38 distinct UTC offsets in use, not 24. Here's the full breakdown.
The BasicsWhat Is a Half-Hour Time Zone?
Countries like India and Iran use UTC offsets ending in :30. Here's why half-hour (and even quarter-hour) time zones exist and which countries use them.
Clock ChangesWhat Is Daylight Saving Time?
Daylight saving time shifts clocks forward by one hour in spring and back in fall. Here's what it is, when it happens, and which countries observe it.
Clock ChangesWhy Does Daylight Saving Time Exist?
DST was invented to save energy and make better use of daylight hours. But does it actually work? Here's the full history and modern evidence.
Clock ChangesWhich Countries Use Daylight Saving Time?
About 70 countries observe DST — but most of the world doesn't. Here's a breakdown of who changes their clocks and who doesn't, and why.
Clock ChangesEST vs EDT: What's the Difference?
EST is Eastern Standard Time (UTC−5). EDT is Eastern Daylight Time (UTC−4). Here's when each applies and which US states use them.
Clock ChangesPST vs PDT: What's the Difference?
PST is Pacific Standard Time (UTC−8). PDT is Pacific Daylight Time (UTC−7). Here's the full breakdown of when each is active and which regions use them.
Clock ChangesCST vs CDT: What's the Difference?
CST is Central Standard Time (UTC−6). CDT is Central Daylight Time (UTC−5). Here's who uses them and when they switch.
Clock ChangesMST vs MDT — and the Arizona Exception
MST is Mountain Standard Time (UTC−7). MDT is Mountain Daylight Time (UTC−6). But Arizona stays on MST year-round — with one famous exception.
Clock ChangesWhen Does Daylight Saving Time Start and End?
DST dates differ between the US, Europe, and the Southern Hemisphere. Here are the exact rules and how to find out when your region's clocks change.
Clock ChangesUS States That Don't Observe Daylight Saving Time
Arizona and Hawaii don't change their clocks. Here's the full list of US states and territories that stay on standard time year-round and why they opted out.
Work & TravelBest Times to Schedule Meetings Across Time Zones
There is no perfect meeting time that works for everyone — but there are windows that minimize the pain. Here's how to find them.
Work & TravelHow to Schedule Meetings Between the US and Europe
The US–Europe time gap creates a narrow overlap window. Here's exactly when to schedule, what to avoid, and how to make cross-Atlantic meetings less painful.
Work & TravelBest Meeting Times for US and Asia Teams
The US–Asia gap of 12–16 hours makes real-time overlap nearly impossible. Here are the best windows, workarounds, and async strategies that actually work.
Work & TravelHow to Convert Working Hours Between Time Zones
A practical guide to converting 9-to-5 working hours across any two time zones, including mental math shortcuts and the common mistakes to avoid.
Work & TravelHow to Run Async Teams Across Time Zones
The best distributed teams design for async by default. Here's how to structure communication, decisions, and workflows so time zones stop being a blocker.
Work & TravelTime Zone Etiquette for Remote Teams
Small habits around time zones — how you write times, schedule meetings, and communicate across offices — have an outsized effect on team culture. Here's what good looks like.
Deep DivesIANA Time Zone Database Explained
The IANA tz database is the source of truth for time zone rules used by virtually every operating system and programming language. Here's how it works.
Deep DivesUTC vs GMT: What's Actually Different?
UTC and GMT are often used interchangeably, but they're technically distinct. Here's what separates them and when the difference actually matters.
Deep DivesUnix Time vs UTC
Unix time is the number of seconds since January 1, 1970 — but it's not the same as UTC. Here's how Unix timestamps work and why they ignore leap seconds.
Deep DivesISO 8601 Date and Time Format Explained
ISO 8601 is the international standard for representing dates and times in software. Here's how to read and write it correctly, and why it matters.
Deep DivesHow Computers Handle Time Zones
From the system clock to what's displayed on your screen, here's the full chain of how operating systems and applications manage time zone conversions.
Deep DivesWhat Is a POSIX Time Zone String?
POSIX TZ strings like 'EST5EDT,M3.2.0,M11.1.0' encode time zone rules in a compact format. Here's how to read them and when you'll encounter them.
Deep DivesNTP: How Computers Stay in Sync
The Network Time Protocol keeps billions of computers' clocks accurate to within milliseconds of each other. Here's how it works and why it matters.
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