How to Convert Time Zones (UTC Offsets Explained)

By HSP · Published October 13, 2026 · 3 min read · Conversions

Flat world map for travel time zones — Photo: “World map of bathymetric data - GEBCO 2014” by GEBCO world map 2014 (public domain) · CC0 1.0 · via Openverse (wikimedia)

Short answer

Convert time zones by expressing both sides in UTC, then applying each offset (and DST). Example: 15:00 in London (UTC+0 winter) is 10:00 in New York (UTC−5).

Time zone math fails when you ignore daylight saving. Always convert through UTC or use a tool that knows IANA zone names. Try the time zone converter.

UTC offsets

UTC is the reference. New York is UTC−5 in standard time and UTC−4 in daylight time. India Standard Time stays UTC+5:30 year-round.

Worked example

A call at 9:00 America/New_York in July (EDT, UTC−4) is 13:00 UTC, which is 18:30 in India (UTC+5:30) and 14:00 in London (BST, UTC+1).

Scheduling teams

For three or more cities, a grid beats mental math — use the meeting planner worldwide view. Related: plan a meeting across time zones.

Date line caveats

Crossing the International Date Line can change the calendar day. The date difference calculator helps with multi-day spans.

More worked numbers

Change one input at a time so you build intuition. Write the formula, substitute values, then confirm with the free timezone converter. If the tool disagrees with your hand math, check units first (months vs years, percent vs decimal, inclusive ranges).

Common mistakes to avoid

Mixing up percent and decimal forms (15% is 0.15, not 15).
Using the wrong base when calculating a change or a reverse percentage.
Ignoring fees, tax or daylight saving when the real-world total depends on them.
Rounding too early in multi-step arithmetic.

How to practise

Invent three mini-problems from your own life — a bill, a grade, a trip, a loan quote — and solve them on paper before you open the calculator. Teaching the steps to someone else is one of the fastest ways to lock in the method.

After you finish this guide, explore the linked tools above and the related articles for neighbouring skills. Our calculators run privately in your browser with no sign-up, so you can check homework, budgets or work estimates without uploading data.

Quick reference card

Keep the short answer box at the top of this page as your cheat sheet. When a search result brought you here for a specific phrase, that box is designed to match the query with the formula first, then the examples below fill in the judgement calls.

Frequently asked questions

How do I convert time zones manually?

Convert the local time to UTC by removing the offset, then add the destination offset. Watch DST. Double-check units and confirm with the linked tool on this page before you rely on the figure for money or school decisions.

What is UTC?

Coordinated Universal Time — the global reference clock for civil time zones. Double-check units and confirm with the linked tool on this page before you rely on the figure for money or school decisions.

Does India observe daylight saving?

No. India stays on UTC+5:30 all year. Double-check units and confirm with the linked tool on this page before you rely on the figure for money or school decisions.

What tool should I use for teams?

The meeting planner for overlap; the time zone converter for one-off conversions. Double-check units and confirm with the linked tool on this page before you rely on the figure for money or school decisions.