Timezone Knowledge & Reference Guides
Understand how time zones work around the world.
- A Brief History of Time ZonesTrace the history of time zones from local solar time through the 1884 International Meridian Conference to the modern IANA database, and learn how political decisions continue to reshape the map.
- What Is UTC? The World's Time Standard ExplainedA complete explanation of Coordinated Universal Time (UTC): how it works, why it replaced GMT as the global standard, and how it affects international scheduling.
- Military Time Zones and the NATO Phonetic SystemLearn the A-through-Z military time zone system, why UTC is called Zulu time, and how NATO letter designations are used in aviation, maritime, and military operations.
- UTC Offset Explained: What the Numbers MeanA clear explanation of what UTC offsets are, how to read them, why they change with daylight saving time, and how to use them reliably for international scheduling.
- How Time Zones Are DeterminedUnderstand how time zones are set by geography, politics, and economics — and why so many countries use offsets that deviate from the simple 15-degree rule.
- Half-Hour and Quarter-Hour Time ZonesDiscover the time zones that use 30-minute and 45-minute offsets from UTC, including India, Nepal, Iran, Myanmar, and the Chatham Islands, and learn why they exist.
- Why Do Time Zones Exist?Learn why the world is divided into time zones, how railroads and global communication drove their creation, and how the modern system of 24 zones was established.
- Working Hours in Los Angeles: A Timezone GuideA complete guide to Los Angeles business hours, Pacific Time UTC offsets, DST transitions, and the best windows for scheduling calls with LA-based teams.
- US Time Zones ExplainedA complete guide to the six US time zones, DST exceptions in Arizona and Hawaii, Indiana’s complicated history, and time zones in US territories.
- Working Hours in Chicago: A Timezone GuideA complete guide to Chicago business hours, Central Time UTC offsets, DST transitions, and the best windows for scheduling calls with Chicago-based teams.
- Working Hours in San Francisco: A Timezone GuideEverything you need to know about San Francisco business hours, Pacific Time UTC offsets, DST transitions, and the best corridors for scheduling calls with SF-based teams.
- Central European Time (CET) ExplainedLearn how Central European Time (CET, UTC+1) and Central European Summer Time (CEST, UTC+2) work, which countries use them, and how DST affects pan-European scheduling.
- Working Hours in Zurich: A Timezone GuideZurich uses CET (UTC+1) in winter and CEST (UTC+2) in summer. This guide covers Swiss business hours, banking sector schedules, and scheduling windows between Zurich and cities in the US, UK, and Asia.
- Working Hours in Amsterdam: A Timezone GuideAmsterdam uses CET (UTC+1) in winter and CEST (UTC+2) in summer. This guide covers Dutch business hours, work-life balance norms, and scheduling windows between Amsterdam and cities in the Americas, UK, and Asia.
- Australian Time Zones ExplainedA comprehensive guide to Australian time zones, covering AEST, ACST, and AWST, the unusual 30-minute and 45-minute offsets, which states observe DST, and scheduling tips.
- Working Hours in Seoul: A Timezone GuideSeoul uses Korea Standard Time (KST, UTC+9) year-round with no daylight saving time. This guide covers Korean business hours, hierarchical meeting culture, and scheduling windows with the US, Europe, and Asia.
- Working Hours in Shanghai: A Timezone GuideShanghai uses China Standard Time (CST, UTC+8) year-round with no daylight saving time. This guide covers Chinese business hours, the single national time zone policy, and scheduling windows with Europe and the Americas.
- Japan Standard Time (JST) ExplainedA complete guide to Japan Standard Time (UTC+9): why Japan abandoned daylight saving time after WWII, how JST shapes business culture, and what developers need to know about JST in servers and logs.
- Working Hours in Mexico City: A Timezone GuideMexico City uses Central Standard Time (CST, UTC−6) in winter and Central Daylight Time (CDT, UTC−5) in summer. This guide covers Mexican business hours, mealtime culture, and scheduling with North America and Europe.
- Working Hours in São Paulo: A Timezone GuideSão Paulo operates on Brasília Time (BRT, UTC−3) year-round since Brazil abolished daylight saving time in 2019. This guide covers Brazilian business hours and scheduling windows with North America and Europe.