Time zones and clocks
Why some time zones are offset by 30 or 45 minutes
Most of the world runs on whole-hour offsets from UTC. A dozen or so places do not, and each one has a reason, usually a meridian that fell awkwardly between two hour lines.
Last reviewed October 5, 2026About 3 min to readSite version v2026.10.1
Where the half hours come from
A time zone is meant to keep clock noon close to solar noon, and solar noon moves four minutes for every degree of longitude. A country whose centre sits near a 15-degree meridian gets a tidy whole-hour offset. A country whose centre sits roughly halfway between two of those meridians faces a choice: pick one and accept that noon is half an hour off across the whole country, or split the difference.
India is the clearest example. Its reference meridian, 82.5 degrees east, lies exactly between the 75-degree and 90-degree lines, so Indian Standard Time is UTC+5:30. The same arithmetic produced Iran (UTC+3:30), Afghanistan (UTC+4:30), Myanmar (UTC+6:30) and Sri Lanka (UTC+5:30, matching India since 2006).
The odd offsets in use today
| Place | Offset | Note |
|---|---|---|
| India, Sri Lanka | UTC+5:30 | No daylight saving; about 1.4 billion people share this offset. |
| Nepal | UTC+5:45 | Based on the meridian of Kathmandu, adopted in 1986. Fifteen minutes ahead of India. |
| Iran | UTC+3:30 | Seasonal changes were abolished in 2022, so the offset is now fixed. |
| Afghanistan | UTC+4:30 | Thirty minutes ahead of Pakistan on its eastern border. |
| Myanmar | UTC+6:30 | Shared with the Cocos (Keeling) Islands. |
| Newfoundland, Canada | UTC-3:30 | UTC-2:30 in summer. The only half-hour zone in North America. |
| Central Australia | UTC+9:30 | South Australia changes to UTC+10:30 in summer; the Northern Territory does not. |
| Marquesas Islands, French Polynesia | UTC-9:30 | Thirty minutes ahead of Tahiti. |
| Chatham Islands, New Zealand | UTC+12:45 | UTC+13:45 in summer. Forty-five minutes ahead of the mainland. |
| Eucla, Western Australia | UTC+8:45 | Unofficial but long established, and recorded in the time zone database. |
| Lord Howe Island, Australia | UTC+10:30 | The only zone whose daylight saving shift is 30 minutes rather than 60, to UTC+11. |
Several offsets have come and gone. Venezuela ran on UTC-4:30 from 2007 to 2016 before returning to UTC-4. North Korea moved to UTC+8:30 in 2015 and back to UTC+9 in 2018 to match the South. The time zone database keeps all of these in its history, which is why a timestamp from Caracas in 2010 still converts correctly today.
The 45-minute cases
Nepal's offset of UTC+5:45 is set from the meridian of Kathmandu, at about 85.3 degrees east, rounded to the nearest quarter hour. It is deliberately not India's UTC+5:30: the quarter-hour difference is a small, visible assertion that Nepal keeps its own time. The practical effect is that noon in Kathmandu is 12:15 PM in Delhi and 6:15 AM in London.
The Chatham Islands, 800 kilometres east of New Zealand's South Island, keep UTC+12:45, 45 minutes ahead of the mainland, and shift to UTC+13:45 with the rest of the country in summer. Eucla, a tiny community straddling the Western Australia and South Australia border, sits on UTC+8:45 by local custom rather than law, splitting the 90-minute gap between the two states it sits between.
How to convert with them without slipping
Odd offsets trip people up because the mental shortcut "add N hours" no longer works. The safe method is still the same: convert to UTC first, then to the target. 9:00 AM in Mumbai is 03:30 UTC, which is 10:30 PM the previous evening in New York during winter. Note the date change: it is the half hour, not a whole hour, that pushes the New York reading across midnight.
The converter handles every one of these offsets and shows the local date next to each clock, with a Today, Tomorrow or Yesterday marker relative to your own zone. The IST abbreviation page covers the one code in this list that is also ambiguous, since IST can mean Indian, Irish or Israel Standard Time.
See it on the site
- Time in IndiaThe live IST clock with UTC comparison tables for January and July.
- Time in NepalThe only country on a 45-minute offset, with sunrise and sunset through the year.
- IST to EST chartAn hour-by-hour table that shows how a half-hour offset crosses the date line.