Time Zone Calculator

Convert · UTC offset · Meeting planner

Date and time

Date

Time

From zone

City / IANA zone

To zone

City / IANA zone

Quick examples

📌

Uses IANA names (e.g. America/New_York). Offsets follow your browser zone data for the chosen date.

🌍 Pick zones and a date to convert local time and compare UTC offsets.

Time Zone Conversion Method

Local wall clock time is not enough. You need a zone identity and a date so daylight saving rules can apply.

Convert between zones

UTC = wall_time_in_source − offset(source, date) Then: wall_time_in_target = UTC + offset(target, date) Example: 09:00 in America/New_York in January (UTC−5) → 14:00 UTC → 19:00 in Europe/London (UTC+0)

Hour difference

Δhours = offset_B − offset_A If B is ahead of A, Δ is positive Offsets are for the same UTC instant

💡

Prefer IANA names over EST/PST. Those abbreviations collide across regions.

Common UTC Offsets

City (IANA)	Typical winter	Typical summer
New York	UTC−5	UTC−4
Los Angeles	UTC−8	UTC−7
London	UTC+0	UTC+1
Paris	UTC+1	UTC+2
Kolkata	UTC+5:30	UTC+5:30
Tokyo	UTC+9	UTC+9
Sydney	UTC+11	UTC+10*

*Southern Hemisphere seasons reverse relative to northern summer labels. Always check the date.

How do you convert time between time zones?

Map the source local time to a UTC instant using that zone offset, then format the instant in the destination zone.

What is the difference between UTC and GMT?

UTC is the modern civil time standard. GMT is a historical Greenwich mean time label often treated as UTC+00 in everyday speech.

How to Use This Time Zone Calculator

Choose Convert to turn a local date and time in one city into another city clock. Choose Difference to focus on the hour gap between two zones on a date. Choose Meeting to broadcast one meeting time into up to four zones. Choose World clock to see “now” across your selected zones.

Pick IANA zones from the lists. Enter the date when daylight saving might matter. Results show local times, UTC, abbreviations, weekday labels, and a chart of offsets.

What is a time zone?

A time zone is a region that shares the same legal civil time rules for a period of history. Those rules include a standard UTC offset and optional daylight saving transitions. The IANA Time Zone Database publishes machine readable rules for many locations under names such as America/Chicago.

What is UTC?

Coordinated Universal Time (UTC) is the time scale used as the reference for civil clocks worldwide. Zone offsets are expressed relative to UTC. Timing laboratories contribute to UTC. When you convert zones, you are really moving through a shared UTC instant.

How to convert time zones manually

1. Write the source local date and time. 2. Look up the source offset for that date (including DST if any). 3. Subtract the offset to reach UTC. 4. Add the destination offset for the same UTC instant. 5. Adjust the calendar date if the clock crosses midnight.

Worked example: 15:00 on 15 January in Asia/Kolkata (UTC+5:30) is 09:30 UTC. In America/New_York that January day is UTC−5, so local time is 04:30 the same calendar date.

Daylight saving time

Many jurisdictions advance clocks in warmer months. The hour gap between New York and London is often five hours in winter and five or four hours depending on transition weeks when one side has changed and the other has not. Always convert with a concrete date near travel or meeting plans.

Why abbreviations fail

IST can mean India Standard Time or Israel Standard Time. CST can mean Central Standard Time in North America or China Standard Time. IANA identifiers remove that ambiguity for software and for this calculator.

Meeting planner tips

Anchor the meeting in one zone that owns the agenda. Check whether any city falls outside typical work hours (for example before 08:00 or after 20:00 local). The Meeting mode lists four local clocks for one UTC instant so everyone shares the same event.

Common mistakes

Using EST year round for New York
Ignoring the date near DST changes
Confusing UTC with a city that observes DST
Assuming every zone is a whole number of hours (India is +5:30)
Comparing ambiguous abbreviations across countries

Practical scenarios

Remote teams schedule standups. Travelers convert flight arrival boards. Support desks publish follow the sun handoff windows. Broadcasters time live events for multiple markets.

When this calculator is useful

Use it for one off conversions, offset checks, and multi city meeting snapshots without opening a full calendar product.

When this calculator may not be enough

It does not replace a calendar that sends invites with embedded zone IDs. It does not forecast future law changes beyond the zone data already installed in your browser. Extremely historical dates may be incomplete in some engines.

How to interpret your result

The hero shows the primary target local time (or the hour gap in Difference mode). Chips show offsets and the signed gap. Metrics include UTC and weekday labels so you can spot date line crossings.

UTC versus local clocks

Servers and logs often store UTC. Humans read local time. Convert at the edges: store UTC, display with an IANA zone. This calculator demonstrates that edge conversion.

Half hour and 45 minute offsets

Not every zone differs by whole hours. India (UTC+5:30), Newfoundland (UTC−3:30), and Nepal (UTC+5:45) are common reminders. The gap chip shows fractional hours when needed.

Worked example: New York to Tokyo

Take 09:00 on 10 March in America/New_York. Depending on whether the US spring forward has occurred, the offset is UTC−5 or UTC−4. Tokyo stays UTC+9. If New York is still on UTC−5, UTC is 14:00 and Tokyo is 23:00 the same date. If New York is on UTC−4, UTC is 13:00 and Tokyo is 22:00.

Worked example: meeting across four zones

Fix 16:00 in Europe/London on a June weekday (often UTC+1). That is 15:00 UTC. America/New_York (UTC−4) sees 11:00. Asia/Kolkata (UTC+5:30) sees 20:30. Australia/Sydney depends on its own winter or summer rules for that June date. Meeting mode prints each local clock from one shared UTC instant.

Reference: selected IANA zones

Label	IANA ID
New York	America/New_York
Chicago	America/Chicago
Denver	America/Denver
Los Angeles	America/Los_Angeles
London	Europe/London
Berlin	Europe/Berlin
Kolkata	Asia/Kolkata
Dubai	Asia/Dubai
Singapore	Asia/Singapore
Tokyo	Asia/Tokyo
Sydney	Australia/Sydney
UTC	Etc/UTC

Related calculations

Time zone math pairs with duration tools when you need elapsed hours between two clock readings in one city, and with date tools when meetings cross midnight. A pure time calculator adds or subtracts durations without geography.

Limitations

Results depend on the zone data shipped with your browser and OS. Rare zones or very old dates may differ across platforms. Abbreviations shown are locale dependent short names, not legal definitions.

⚠️

Near DST transitions, some local times are skipped or repeated. Prefer unambiguous UTC for critical systems.

ℹ️

Zone rules follow the IANA Time Zone Database as exposed by your browser. UTC is the civil reference scale used for offsets.

Frequently Asked Questions

How do I find the time difference between two cities?

Select both cities and a date, then read the Gap chip. It is the difference of their UTC offsets at that instant, which can change across DST weeks.

What is an IANA time zone?

It is a named entry in the Time Zone Database such as Europe/Paris. The name carries offset and daylight saving history so software can compute local time correctly.

Does daylight saving time change the conversion?

Yes. Enter the actual meeting date. The same pair of cities can show different hour gaps before and after each side changes clocks.

Is UTC the same as GMT?

For most everyday conversions people treat GMT as UTC+00. Technical systems should label the scale as UTC and pick an IANA zone for local display.

Why is India 5 hours 30 minutes ahead of UTC?

India Standard Time uses a fixed offset of +5:30 with no daylight saving. Convert by adding five and a half hours to UTC, or use Asia/Kolkata in this tool.

Can I convert EST to PST?

Yes, but select America/New_York and America/Los_Angeles (or other Pacific zones) instead of typing EST or PST alone. The date decides whether each side is on standard or daylight time.

Sources & References

IANA Time Zone Database: iana.org/time-zones
IANA tz link overview (tzdb usage and distribution): data.iana.org/time-zones/tz-link.html
NIST Time and Frequency Division (UTC context): nist.gov/pml/time-and-frequency-division