Timezone Converter

Timezone Converter - Convert Time Between Timezones Instantly

A focused timezone converter that turns a time in one zone into the correct time in another, with automatic daylight-saving handling and a clear time-difference readout. It also tells you whether the converted time lands in working hours, flags weekends, and draws a 24-hour overlap strip showing when both zones are inside business hours — so you can pick a meeting slot that works for everyone. Ideal for international business, remote teams, and travel planning.

How many hours difference between Los Angeles and London?

Los Angeles is 8 hours behind London during winter (LA is UTC-8 PST, London is UTC+0 GMT) and 8 hours behind during summer too — but the transitions to DST are staggered by a couple of weeks, so during late March and late October there are short windows when the gap is 7 hours instead. New York and London differ by 5 hours all year for the same reason. The cleanest way to avoid mistakes around DST transitions is to enter the exact date you care about — this converter applies the correct historical or future offset from the IANA database for that day, including the spring-forward and fall-back boundary hours that some apps mishandle.

How do I pick a meeting time that is in working hours for both zones?

After you convert, the tool shows a meeting-suitability verdict for the target time — Working hours, Early or late, or Likely asleep — and flags the day as a weekend where relevant, so you instantly see whether 14:00 your time lands at 02:00 for the other party. Below that is a 24-hour business-hours overlap strip: it walks every hour of the source day and highlights in green only the hours that fall inside 09:00–17:00 in BOTH zones. If the green band is empty, there is no civil overlap that day and you should rotate the meeting or accept an early/late slot for one side. This is exactly the check that prevents the classic mistake of scheduling a call at 3 a.m. someone's time. The window is computed from the same DST-correct instants used for the conversion, so spring-forward and fall-back days are handled automatically.

Why does the converter sometimes show a different date for the same moment?

The civil calendar date depends on the local time zone, so a single instant in physical time can land on different dates in different cities. When New York is at 23:00 on Monday, Tokyo is already at 12:00 on Tuesday — fourteen hours ahead. Around the international date line the gap reaches 26 hours: when it is 00:00 Friday in Kiribati's Line Islands (UTC+14), American Samoa (UTC-11) is still at 22:00 Wednesday. The converter shows the local date next to each time so you never misread a Tuesday meeting as Monday when it is happening in your time zone.

What is the difference between UTC offset and time zone?

A UTC offset like +05:30 is just a fixed number of hours and minutes from UTC. A time zone is a named geographic region whose offset changes over time according to civil rules — DST, political changes, or historical adjustments. Asia/Kolkata permanently uses +05:30, but America/New_York alternates between -05:00 (standard) and -04:00 (DST). For data storage, always store the IANA zone name (Europe/London) alongside the timestamp rather than only the offset, because the offset alone cannot tell you what the next DST transition will be. RFC 9557 extends ISO 8601 to allow embedding the zone name directly in serialized timestamps.

Why don't all time zones differ by whole hours?

Time zones were originally proposed by Sandford Fleming in 1879 as a neat global grid of 24 one-hour bands, but national borders, political identity, and solar alignment have produced numerous exceptions. India settled on UTC+5:30 in 1906 to give a single midpoint for its wide longitude span; Nepal added an extra 15 minutes to be politically distinct from India. The Chatham Islands of New Zealand use UTC+12:45 because they sit 45 minutes east of mainland NZ in solar time. China unified to a single UTC+8 zone in 1949 despite spanning five geographical hours, so western Xinjiang has solar noon around 15:00 local. France and Spain use Central European Time despite being geographically aligned with Britain — a legacy of the 1940s occupation.

How does daylight saving time complicate conversions?

DST creates two awkward boundary cases per year. In spring, clocks jump from 02:00 to 03:00, so 02:30 simply does not exist that day — a meeting scheduled at that time has to fall on either side. In fall, clocks roll back from 02:00 to 01:00, so 01:30 happens twice. The IANA database resolves these by treating the second instance as the standard-time interpretation, but raw offset arithmetic is ambiguous. This converter snaps your input to a valid instant and warns when you cross a DST boundary, but if you serialize times across DST transitions in your own code, always store the UTC instant plus the zone, never a local time alone.

What is the IANA time zone database and who maintains it?

The IANA Time Zone Database, also called tzdata or the Olson database after its original maintainer Arthur David Olson, is the authoritative source for civil time rules worldwide. It contains the complete UTC offset and DST transition history for every named zone since roughly 1970, plus future scheduled changes. It is updated several times a year (releases like 2026a, 2026b) as governments change DST rules, rename zones, or adjust offsets. The database is in the public domain and is bundled with virtually every operating system, programming language standard library, and browser. Mailing list [email protected] coordinates changes; updates flow into glibc, ICU, Java, Node.js, and Python within days of release.

How precise is JavaScript's time zone conversion in the browser?

Modern browsers use the ICU library bundled with the OS to provide IANA time zone support through Intl.DateTimeFormat and the Temporal API now in Stage 3 of TC39. Accuracy depends on the freshness of the OS's tzdata: a phone or computer that has not been updated may use stale DST rules, especially for countries that change frequently like Russia, Mexico, or Egypt. The Date object stores moments as integer milliseconds since the Unix epoch (1970-01-01T00:00:00Z) with no zone — conversions happen at format time using the system's zone tables. For sub-millisecond timing use performance.now(), which is monotonic and unaffected by NTP adjustments or zone changes; Date.now() can jump backward if the system clock is corrected.

Key Features

• Convert a time from one timezone into another
• Automatic daylight saving time (DST) handling
• Time difference calculator (hours ahead or behind)
• Meeting-suitability verdict: working hours, early/late, or asleep
• Weekend flag for the converted time
• 24-hour business-hours overlap strip for both zones
• Search timezones by city or name
• Popular timezones quick access
• UTC offset display
• Swap source and target with one click
• Copy converted time to clipboard
• Responsive mobile-friendly interface
• Dark mode support
• 100% client-side processing, no server communication