Time Zone Basics

Learn how UTC offsets, daylight saving time, and common city time zones work when scheduling across regions.

Time zones divide Earth into regions that share a civil clock time, usually expressed as an offset from UTC (Coordinated Universal Time).

UTC offsets

Eastern Time is typically UTC−5 (EST) or UTC−4 (EDT). Tokyo is UTC+9 year-round. When scheduling, convert both sides to UTC first to avoid off-by-one-hour mistakes.

Daylight saving time

Many regions shift clocks seasonally. Not every location observes DST, and start/end dates differ by country. Always confirm the city's rules for the date you care about.

Meeting math

A 9:00 AM meeting in New York is mid-afternoon in London during standard overlaps, but the gap shrinks or grows when one side enters DST before the other. Use a converter instead of memorizing.

Tools

Convert times with the time zone converter, count hours with the hours calculator, or track holidays via days until.