Timezone Chaos: A Brief History

  • Before 1883: Every city set its own time by the sun—there were 300+ local times in the US alone!
  • Railways fixed it: Trains needed schedules, so in 1883 the US adopted 4 standard time zones
  • Today: 38 different UTC offsets, but ~200 named timezones (due to DST and political changes)

Weird Timezone Facts

  • China: One timezone for a country spanning 5 geographical zones—9 AM sunrise in the east, noon in the west!
  • India: UTC+5:30 (yes, half hour)—because they split the difference between UTC+5 and UTC+6
  • Nepal: UTC+5:45—just to be 15 minutes ahead of India (seriously)
  • North Korea: Created UTC+8:30 in 2015, then abolished it in 2018 to match South Korea
  • Australia: UTC+8:45 exists for one small region (Eucla), population ~200

The International Date Line

  • Runs through the Pacific Ocean, roughly along 180° longitude
  • Cross westward: Skip a day (Monday → Wednesday)
  • Cross eastward: Repeat a day (Wednesday → Wednesday again)
  • Samoa switched sides in 2011: Skipped December 30 entirely to align with Australia/NZ
  • Fun: You can stand in Tonga (Mon) and see Samoa (Sun) across the water—same moment, different days

Daylight Saving Madness

  • Invented by New Zealand entomologist George Hudson in 1895 (he wanted more evening bug-hunting time)
  • Not everyone uses it: Arizona, Hawaii, most of Asia, Africa, and South America skip DST
  • Australia: Some states observe DST, neighboring states don't—chaos for business
  • 2023: EU voted to abolish DST, but it's stuck in limbo (countries can't agree on permanent winter or summer)
  • The 2:00 AM change: Chosen because few trains run then and bars are closed

UTC vs GMT: What's the Difference?

  • GMT: Greenwich Mean Time—based on solar noon at Royal Observatory, Greenwich, England
  • UTC: Coordinated Universal Time—based on atomic clocks, includes leap seconds
  • Difference: Practically none for most purposes (<1 second), but UTC is the official standard
  • Zulu time: Military/aviation term for UTC (Z = Zulu in NATO phonetic alphabet)

Remote Team Scheduling Tips

  • Golden hours: 9 AM - 11 AM Pacific overlaps with EU afternoon and Asia evening
  • Rotate meeting times: Don't always make the same timezone wake up early
  • Use 'floating time': 'EOD Friday' means different things in different zones—specify a timezone!
  • The '8-hour rule': If team spans 8+ hours, async communication beats meetings
  • Calendar apps: Always send invites with timezone—never just 'Let's meet at 3 PM'

Timezone Abbreviations Decoded

  • PST/PDT: Pacific Standard/Daylight Time (UTC-8/-7) — California, Seattle
  • EST/EDT: Eastern Standard/Daylight Time (UTC-5/-4) — New York, Miami
  • GMT/BST: Greenwich Mean/British Summer Time (UTC+0/+1) — London
  • CET/CEST: Central European Time/Summer (UTC+1/+2) — Berlin, Paris
  • JST: Japan Standard Time (UTC+9) — No DST, stays +9 year-round
  • IST: Ambiguous! India (UTC+5:30), Israel (UTC+2/+3), or Ireland (UTC+0/+1)

Developer Timezone Tips

  • Store everything in UTC: Convert to local only for display
  • Use IANA names: 'America/New_York' not 'EST' (EST ignores DST)
  • JavaScript quirk: new Date() uses local time, but .toISOString() outputs UTC
  • Database: PostgreSQL TIMESTAMPTZ is your friend, MySQL TIMESTAMP... less so
  • Cron jobs: Specify timezone explicitly—server might not be in your zone