Time Difference Calculator

How This IANA Time Difference Calculator Works

This calculator computes the exact minute offset between any two IANA time zones at your chosen date and local time by evaluating both zones against the official IANA Time Zone Database (tzdb) via the browser’s Intl.DateTimeFormat engine. Because it calculates offsets in total minutes rather than rounding to whole hours, it accurately handles every 30-minute and 45-minute time zone worldwide as well as historical and upcoming Daylight Saving Time transitions.

Why Time Differences Must Be Measured in Minutes

Most world time zones sit an integer number of hours ahead of or behind Coordinated Universal Time (UTC), but several major countries and territories use half-hour or three-quarter-hour offsets:

• Half-Hour Offsets (30 Minutes): India (Asia/Kolkata, UTC+05:30), Sri Lanka (Asia/Colombo, UTC+05:30), Newfoundland in Canada (America/St_Johns, UTC−03:30 standard / −02:30 DST), South Australia and the Northern Territory (Australia/Adelaide and Australia/Darwin, UTC+09:30 / +10:30), Iran (Asia/Tehran, UTC+03:30), Afghanistan (Asia/Kabul, UTC+04:30), Myanmar (Asia/Yangon, UTC+06:30), and the Marquesas Islands (Pacific/Marquesas, UTC−09:30).
• Quarter-Hour Offsets (45 Minutes): Nepal (Asia/Kathmandu, UTC+05:45), New Zealand’s Chatham Islands (Pacific/Chatham, UTC+12:45 standard / +13:45 DST), and Eucla in Western Australia (Australia/Eucla, UTC+08:45).

How Daylight Saving Time Shifts the Time Difference Between Cities

Two regions rarely start or end Daylight Saving Time on the same date. For example, the United States and Canada begin DST on the second Sunday in March and return to standard time on the first Sunday in November, whereas the United Kingdom and European Union begin on the last Sunday in March and end on the last Sunday in October. During those one-to-three-week gap windows in March, October, and November, the time difference between New York and London narrows from 5 hours to 4 hours. Meanwhile, comparing a DST-observing city like Los Angeles (America/Los_Angeles) with non-DST Phoenix (America/Phoenix) switches from a 1-hour difference in winter to 0 hours in summer. See all U.S. zones on the U.S. Time Zone Map or check your local zone on What Time Zone Am I In?.