Timezone Converter

Understanding Timezones

The world is divided into 24 primary time zones, each roughly 15° of longitude wide. The reference point is Coordinated Universal Time (UTC, formerly GMT), which is the time at the Prime Meridian (0° longitude) in Greenwich, London.

UTC Offsets

Each timezone is defined as UTC+X or UTC−X, where X is the number of hours (and sometimes half-hours) from UTC. For example, India Standard Time (IST) is UTC+5:30, Nepal is UTC+5:45, and US Eastern Standard Time is UTC−5.

Daylight Saving Time (DST)

Many countries observe DST — advancing clocks by one hour in spring and reverting in autumn. This is done to make better use of daylight in evenings. This tool uses your browser's built-in Intl.DateTimeFormat API which automatically accounts for DST transitions for all IANA timezone identifiers.

IANA Timezone Database

The IANA (Internet Assigned Numbers Authority) timezone database is the globally accepted standard for timezone definitions. Timezones are identified by region/city (e.g., "America/New_York", "Asia/Kolkata"). The database is updated regularly to reflect political changes in DST rules worldwide.

Common Scheduling Pitfalls

• The US and EU change clocks on different dates — there's a 1–2 week period each year where offsets differ from normal.
• India, China, and several other large countries use a single timezone despite their geographic span.
• Some timezones are offset by 30 or 45 minutes (India +5:30, Nepal +5:45, Iran +3:30).
• Arizona (US) does not observe DST, unlike the rest of the Mountain Time Zone.