OmniTools

Time Zone & World Clock Converter

Compare global city time zones and find optimal meeting overlap slots.

Basis: IANA time zone database (tzdata) via the browser's ECMA-402 Intl implementation·2026-08-28 verified·Editorial policy

Before you rely on this

Uses the IANA time zone database through the browser's Intl API, so daylight saving rules and transition dates are handled automatically. When a country changes its rules, however, the old rules apply until the browser's data is updated.

Tool Overview & Key Purpose

Compare world clock time zones and find optimal overlapping hours for global business meetings.

Step-by-Step Usage Instructions

1STEP 1

Set home baseline city (e.g. Seoul KST or New York EST) and desired date/time.

2STEP 2

Add target participant cities (London, San Francisco, Tokyo, Sydney, Paris).

3STEP 3

Drag the 24-hour interactive slider to observe corresponding times across all cities.

4STEP 4

Identify green overlap windows matching mutual business working hours (9 AM - 6 PM).

Real-World Scenarios & Practical Cases

3 Practical CasesScenario #1

US West Coast & Korea Sync Meeting

Seoul 9:00 AM KST corresponds to San Francisco 4:00 PM PST the previous day, allowing smooth overlapping business hours.

Morning in Asia aligns with late afternoon in US West Coast.Scenario #2

Daylight Saving Time (DST) Shift Verification

Automatically adjusts for March/November Daylight Saving Time shifts to prevent scheduling errors.

Eliminate confusion during DST transition weeks.Scenario #3

US Stock Market (NYSE/NASDAQ) Hours Tracking

US market opening (9:30 AM EST) mapped to local time zones worldwide.

Essential for international stock market traders.Time zone data sourceUTC offset calculation engine with integrated regional Daylight Saving Time rules.

Pro Tips & Key Considerations

Korea (KST) and Japan (JST) are UTC+9 and do not observe Daylight Saving Time.US Pacific Time is UTC-8 (PST) / UTC-7 (PDT); Eastern Time is UTC-5 (EST) / UTC-4 (EDT).

Frequently Asked Questions (FAQ)

Sources & References

IANA Time Zone Database Official U.S. Time (NIST)

Basis: IANA time zone database (tzdata) via the browser's ECMA-402 Intl implementation · 2026-08-28 verified