Timezone Converter — Free Online Tool

What is Timezone Converter & World Clock (IANA, UTC Offset, DST)?

Timezone converter translates time between timezones (IANA database: America/New_York, Europe/London, Asia/Tokyo), handling UTC offsets, daylight saving time (DST), and timezone abbreviations (EST, PST, GMT). Convert: 3:00 PM EST → 8:00 PM GMT (5-hour difference), schedule meetings across timezones (10 AM in NYC = 3 PM in London), compare world clocks (current time in 10+ cities). Tool shows: timezone full name (Eastern Standard Time), UTC offset (UTC-5 or UTC+0), DST status (active/inactive), timezone abbreviation (EST vs EDT), date line crossings (Mon 10 PM in LA = Tue 5 PM in Tokyo). Useful for: remote teams (coordinate meeting times across US/Europe/Asia), travel planning (flight times, jet lag calculation), event scheduling (webinar at 2 PM PST = ? in attendee's timezone), API timestamps (convert local time to UTC for storage). Works offline (IANA timezone database bundled), supports 400+ timezones.

• IANA timezone database: 400+ timezones: America/New_York (EST/EDT), Europe/London (GMT/BST), Asia/Tokyo (JST), Australia/Sydney (AEDT/AEST). Format: Continent/City. Handles DST rules (spring forward, fall back).
• UTC offset calculation: Shows offset from UTC: New York = UTC-5 (winter, EST) or UTC-4 (summer, EDT). London = UTC+0 (winter, GMT) or UTC+1 (summer, BST). Offset changes with DST.
• DST awareness: Automatically applies DST rules: US (second Sunday March → first Sunday November), Europe (last Sunday March → last Sunday October). Shows if DST active (EDT vs EST).
• Date line handling: International Date Line: crossing changes date. Example: Monday 11 PM in Honolulu (UTC-10) = Tuesday 9 AM in Tokyo (UTC+9). 19-hour difference, date changes.
• Meeting scheduler: Find common meeting time: 9 AM–5 PM in NYC, 2 PM–10 PM in London, 10 PM–6 AM in Tokyo. Tool highlights overlaps (2 PM–5 PM NYC = 7 PM–10 PM London, but midnight in Tokyo).

Why use timezone converter?

Calculating timezone differences manually is error-prone (DST changes, UTC offsets, date line crossings). This tool handles all edge cases.

• Avoid DST mistakes: DST changes twice yearly (spring forward, fall back). Forgetting DST = 1-hour error. Tool auto-detects DST (shows EDT vs EST, BST vs GMT). No manual offset calculation.
• Schedule global meetings: Remote teams across timezones: 10 AM in NYC = ? in London, Tokyo, Sydney. Tool shows all conversions instantly. Avoid scheduling midnight meetings (9 AM in NYC = midnight in Tokyo).
• Handle date line crossings: Date line separates timezones (Monday in LA can be Tuesday in Tokyo). Manual calculation confusing. Tool shows date changes (Mon 10 PM LA = Tue 5 PM Tokyo).
• Compare UTC offsets: UTC offset varies by location and season. New York: UTC-5 (winter) vs UTC-4 (summer). London: UTC+0 (winter) vs UTC+1 (summer). Tool shows current offset (auto-updates for DST).
• Convert API timestamps: APIs use UTC (ISO 8601: 2024-01-15T14:30:00Z). Convert to local time for display (UTC 14:30 = 9:30 AM EST). Or convert local input to UTC for storage.
• Travel planning: Flight departs 10 AM NYC, arrives 11 PM London (same day). But 11 PM London = 6 PM NYC (jet lag: 5-hour difference). Tool shows both local times.

When to use timezone converter

Use whenever you need to convert time between timezones or compare world clocks.

• Scheduling meetings across timezones (remote teams: US, Europe, Asia).
• Converting API timestamps (UTC to local time for display, local to UTC for storage).
• Travel planning (flight times, layovers, jet lag calculation).
• Event coordination (webinar at 2 PM PST = ? in Europe, Asia, Australia).
• Comparing world clocks (current time in NYC, London, Tokyo, Sydney).
• Debugging timezone issues (why does date change? DST active or not?).
• Historical time conversions (date in 2020 when DST rules different).
• Learning timezones (understand UTC offsets, DST rules, IANA names).

How to use timezone converter

Select source timezone, time, target timezone, see converted result.

1. Choose source timezone: Select from dropdown: America/New_York (EST/EDT), Europe/London (GMT/BST), Asia/Tokyo (JST), etc. Or search by city name (New York, London, Tokyo). IANA format: Continent/City.
2. Enter time to convert: Input time: 3:00 PM (12-hour format) or 15:00 (24-hour). Select AM/PM if 12-hour. Or use current time (Now button). Optionally select date (for DST accuracy).
3. Choose target timezone(s): Select one or multiple target timezones: Europe/London, Asia/Tokyo, Australia/Sydney. Add multiple for meeting scheduling (compare times across 5+ locations).
4. View converted time: Result shows: time in target timezone (8:00 PM GMT), UTC offset (UTC+0), DST status (GMT or BST), date (if different from source). Example: 3 PM EST → 8 PM GMT (same day).
5. Check DST status: Tool shows if DST active: EST (winter, UTC-5) vs EDT (summer, UTC-4). London: GMT (winter, UTC+0) vs BST (summer, UTC+1). Offset changes automatically.
6. Handle date crossings: If date changes (cross date line), tool shows: Mon 10 PM LA = Tue 5 PM Tokyo. Date diff highlighted (next day, previous day).
7. Schedule meetings (optional): Meeting scheduler mode: enter work hours for each timezone (9 AM–5 PM NYC, 2 PM–10 PM London). Tool highlights overlaps (common meeting window).

Key features

• IANA timezone database: 400+ timezones: America/New_York, Europe/London, Asia/Tokyo. Official IANA names (Continent/City). Updated regularly (DST rule changes).
• DST auto-detection: Automatically applies DST rules (spring forward, fall back). Shows if DST active (EDT vs EST, BST vs GMT). No manual offset adjustment.
• UTC offset display: Shows current UTC offset: New York = UTC-5 (EST) or UTC-4 (EDT). London = UTC+0 (GMT) or UTC+1 (BST). Offset updates with DST.
• Date line handling: Crosses International Date Line (date changes). Example: Monday in LA = Tuesday in Tokyo. Tool shows date difference.
• Multiple conversions: Convert one time to multiple timezones: 3 PM EST → 8 PM GMT, 5 AM JST (next day), 6 AM AEDT (next day). Compare world clocks.
• Meeting scheduler: Find common meeting time across timezones. Input work hours (9 AM–5 PM NYC), see overlaps (2 PM–5 PM NYC = 7 PM–10 PM London).
• Offline support: IANA timezone database bundled (no API). Works offline. Fast, private, always available.

Common use cases

• Meeting across US/Europe: Schedule meeting: 10 AM EST (New York) = 3 PM GMT (London), 7 AM PST (Los Angeles). Tool shows all times. Best window: 2 PM–5 PM EST (7 PM–10 PM GMT, 11 AM–2 PM PST).
• Flight time conversion: Flight departs 10 AM NYC (EST), arrives 11 PM London (GMT). Duration: 13 hours actual (10 AM + 7 hours flight + 5 hours timezone = 11 PM). Tool shows both local times.
• API timestamp (UTC to local): API returns: 2024-01-15T14:30:00Z (UTC). Convert to EST: 9:30 AM (UTC-5). Or EDT: 10:30 AM (UTC-4). Tool detects DST automatically.
• Webinar scheduling: Webinar at 2 PM PST (Pacific). Attendees in EST (5 PM, good), GMT (10 PM, late), JST (6 AM next day, too early). Tool shows all times, highlights issues.
• Date line crossing: Monday 11 PM in Honolulu (UTC-10) = Tuesday 9 AM in Tokyo (UTC+9). 19-hour difference (10 + 9), date changes. Tool shows: Mon 11 PM → Tue 9 AM.
• DST transition: US DST starts: second Sunday in March, 2 AM → 3 AM (spring forward). Convert 2:30 AM EST (doesn't exist) → tool shows gap (2 AM–3 AM skipped). Fall back: 2 AM → 1 AM (repeated hour).

Examples

Timezone conversion examples.

Source: 3:00 PM EST (America/New_York, January), Target: GMT (Europe/London)

8:00 PM GMT (same day). Offset: EST = UTC-5, GMT = UTC+0. Difference: 5 hours. 3 PM + 5 hours = 8 PM.

Source: 3:00 PM EDT (America/New_York, June), Target: BST (Europe/London)

8:00 PM BST (same day). Offset: EDT = UTC-4, BST = UTC+1. Difference: 5 hours. 3 PM + 5 hours = 8 PM.

Source: 10:00 PM PST (America/Los_Angeles, Monday), Target: JST (Asia/Tokyo)

5:00 PM JST (Tuesday). Offset: PST = UTC-8, JST = UTC+9. Difference: 17 hours. 10 PM + 17 hours = 5 PM next day.

Source: 12:00 PM UTC (noon), Targets: EST, PST, GMT, JST

EST: 7 AM (UTC-5), PST: 4 AM (UTC-8), GMT: 12 PM (UTC+0), JST: 9 PM (UTC+9).

Source: 2:30 AM EST (America/New_York, second Sunday March)

Invalid time (doesn't exist). 2 AM → 3 AM (spring forward). 2:30 AM skipped. Tool shows: 2:30 AM EST = 3:30 AM EDT (1 hour ahead).

Technical reference

Timezone technical details (IANA, UTC, DST):

IANA timezone

Format: Continent/City (America/New_York, Europe/London). Continent: America, Europe, Asia, Africa, Australia, Pacific, Antarctica. City: representative city in timezone. ~400 timezones. Updated yearly (DST rule changes).

UTC offset

Offset from UTC (Coordinated Universal Time). Format: UTC±hours (UTC-5, UTC+0, UTC+9). Negative = west of Greenwich, positive = east. Offset changes with DST: EST = UTC-5 (winter), EDT = UTC-4 (summer).

DST rules (US)

Start: second Sunday in March, 2 AM → 3 AM (spring forward, UTC-5 → UTC-4). End: first Sunday in November, 2 AM → 1 AM (fall back, UTC-4 → UTC-5). Affects EST/EDT, PST/PDT, MST/MDT, CST/CDT.

DST rules (Europe)

Start: last Sunday in March, 1 AM UTC → 2 AM (spring forward). End: last Sunday in October, 2 AM UTC → 1 AM (fall back). Affects GMT/BST, CET/CEST, EET/EEST.

Timezone abbreviations

EST (Eastern Standard Time, UTC-5), EDT (Eastern Daylight Time, UTC-4), PST (Pacific Standard Time, UTC-8), PDT (Pacific Daylight Time, UTC-7), GMT (Greenwich Mean Time, UTC+0), BST (British Summer Time, UTC+1), JST (Japan Standard Time, UTC+9, no DST).

Date line

International Date Line (~180° longitude). Cross from west to east = date -1 (back in time). Cross east to west = date +1 (forward in time). Not straight (avoids land, follows boundaries).

ISO 8601 format

Standard: 2024-01-15T14:30:00Z (UTC) or 2024-01-15T09:30:00-05:00 (EST). Z = Zulu (UTC). Offset: -05:00 (5 hours behind UTC). Use for APIs, databases (unambiguous).

Timezone vs offset

Timezone: America/New_York (has DST rules). Offset: UTC-5 or UTC-4 (fixed). Timezone preferred (handles DST automatically). Offset alone = ambiguous (EST or CDT? both UTC-5).

No DST timezones

Some timezones don't use DST: Asia/Tokyo (JST, always UTC+9), America/Phoenix (MST, always UTC-7, Arizona doesn't observe DST), Europe/Moscow (MSK, always UTC+3). Offset never changes.

Historical DST

DST rules change over time. Example: US extended DST in 2007 (Energy Policy Act). Tool uses current rules (2024+). Historical conversions may differ (check past DST dates).

Common mistakes to avoid

Using timezone abbreviations (EST, PST) instead of IANA names (ambiguous)

Why it happens: EST = Eastern Standard Time (UTC-5) OR Australian Eastern Standard Time (UTC+10). PST = Pacific Standard Time (UTC-8) OR Philippine Standard Time (UTC+8). Ambiguous (multiple meanings).

How to avoid it: Use IANA names: America/New_York (not EST), America/Los_Angeles (not PST), Australia/Sydney (not EST). IANA names unambiguous (only one meaning).

Forgetting DST transitions (scheduling meeting during non-existent time)

Why it happens: DST spring forward: 2 AM → 3 AM (2 AM–3 AM doesn't exist). Scheduling 2:30 AM meeting = invalid time (clocks skip 2:30 AM). Common mistake when scheduling across timezones.

How to avoid it: Use timezone tool to check time validity. Or avoid DST transition hours (2 AM–3 AM in US, 1 AM–2 AM in Europe). Schedule meetings during business hours (9 AM–5 PM, safe).

Using UTC offset instead of timezone (doesn't handle DST)

Why it happens: UTC-5 = EST (winter) or CDT (summer, Central Daylight Time). Offset alone doesn't specify which. Storing UTC-5 in database = ambiguous (EST or CDT?).

How to avoid it: Store IANA timezone: America/New_York (handles DST automatically). Convert to UTC offset when displaying. Or store timestamps in UTC (ISO 8601: 2024-01-15T14:30:00Z), convert to local for display.

Not accounting for date line (wrong date in conversions)

Why it happens: Date line crossing changes date. Monday 10 PM LA = Tuesday 5 PM Tokyo. Forgetting date change = scheduling Tuesday meeting when it's actually Wednesday in Tokyo.

How to avoid it: Use tool to check date. Or remember: crossing date line east to west = date +1 (next day), west to east = date -1 (previous day). Pacific islands (UTC+12) can be 1 day ahead of UTC.

Assuming all countries observe DST (many don't)

Why it happens: Japan, China, India, most of Africa, parts of Australia (Queensland) don't use DST. Assuming DST = wrong offset. Example: Japan always UTC+9 (no summer/winter change).

How to avoid it: Check if timezone observes DST. Tool shows DST status (active/inactive). Countries without DST: timezone offset never changes (always UTC+9 for Japan).

Frequently asked questions

What is the difference between UTC and GMT?

UTC (Coordinated Universal Time) = time standard (atomic clocks, no DST). GMT (Greenwich Mean Time) = timezone (UTC+0 in winter, but UK uses BST = UTC+1 in summer). UTC = reference, GMT = timezone. Use UTC for precision.

Why do some timezones have half-hour or 45-minute offsets?

India = UTC+5:30, Nepal = UTC+5:45, Australia (Adelaide) = UTC+9:30. Historical reasons (local solar time, political boundaries). Not all timezones whole hours. Tool handles fractional offsets.

What happens during DST transitions (spring forward, fall back)?

Spring forward: 2 AM → 3 AM (2 AM–3 AM doesn't exist, clocks skip). Fall back: 2 AM → 1 AM (1 AM–2 AM repeated, clocks go back). Scheduling during transition = issues (non-existent time or ambiguous time).

How do I convert time for APIs (local to UTC)?

ISO 8601 format: 2024-01-15T14:30:00Z (UTC) or 2024-01-15T09:30:00-05:00 (with offset). Store in UTC (Z), display in local timezone. Tool converts local → UTC for storage.

Why does the date change when crossing the International Date Line?

Date line = ~180° longitude (opposite side of Earth from Greenwich). Cross west to east = date -1 (back in time). Cross east to west = date +1 (forward in time). Prevents confusion (ensures date consistent in each timezone).

What is IANA timezone database and why use it?

IANA (Internet Assigned Numbers Authority) maintains official timezone database (400+ timezones). Format: Continent/City (America/New_York). Includes DST rules, historical changes. Standard for computers (Linux, macOS, programming languages).

How do I handle timezones that don't observe DST?

Timezones without DST: offset never changes. Japan = always UTC+9, Arizona = always UTC-7. No spring forward/fall back. Simpler (no DST transitions), but difference with DST timezones changes (EST = UTC-5 winter, UTC-4 summer).

References

• IANA Timezone Database
• Daylight Saving Time Rules
• ISO 8601 Standard
• World Time Zones