Understanding Time Zones (and Why They’re Weird)

TL;DR

Time zones exist to align clock time with daylight, but political borders, daylight-saving policies, and historical compromises make them surprisingly messy. Anchor your planning around Coordinated Universal Time (UTC) and double-check offset changes during seasonal transitions.

A brief history of timekeeping

Before trains and telegraphs, towns simply set clocks by the sun. Railroads needed standardized schedules, so nations adopted time zones anchored to Greenwich, London—the reference for Longitude 0°. Coordinated Universal Time (UTC) succeeded Greenwich Mean Time in 1960 and is the modern baseline for civil time.

Offsets and daylight saving time

UTC offsets describe how many hours a local zone sits ahead or behind UTC. New York is typically UTC-05:00, London is UTC+00:00, and Sydney is UTC+10:00. The plot twist is daylight saving time (DST). Many regions shift clocks forward in spring and back in autumn, but not on the same dates. Arizona ignores DST entirely, Brazil abandoned it in 2019, and the European Union is debating whether to keep it. Always confirm the offset for specific dates rather than assuming it never changes.

Practical travel and teamwork tips

• Convert to UTC first, then to the target zone when scheduling meetings or flights.
• Share invites using ISO 8601 format (e.g., 2025-10-12T09:00Z) so calendar apps translate automatically.
• Watch out for countries that use half-hour or 45-minute offsets, such as India (UTC+05:30) and Nepal (UTC+05:45).
• When coordinating launches or support coverage, plan a DST “audit” twice a year to verify handoff times.

Make the world clock your ally

AtlasCalc’s World Time tool caches live data and highlights key cities so you can sanity-check offsets and handoffs in seconds. Combine it with alerts in your calendar for effortless follow-the-sun coordination.