Understand time

Time & Date Guides

Plain-language explanations for time zones, UTC, calendars and date math.

What Is UTC?

Understand Coordinated Universal Time and why the world uses it as a common reference.

Learn the practical and technical difference between UTC and Greenwich Mean Time.

A clear explanation of offsets, IANA zone IDs and why locations change clocks.

How daylight saving time changes local clocks and affects planning.

How ISO 8601 numbers weeks and handles dates near New Year.

Count weekdays while accounting for configurable weekends and public holidays.

Understand offsets, political boundaries and the database rules behind local time.

Follow what happens when clocks move forward or back and how software handles the transition.

Compare two places correctly when their offsets or calendar dates differ.

Geography, trade, politics and history all shape the clocks countries choose.