Half-hour and 45-minute time zones
14 of the 312 zones in the tz database keep a standard time that is not a whole number of hours from UTC: 11 sit on the half hour and 3 on a 45-minute mark. Since 1970 another 12 zones used such an offset for a while and then moved to a whole hour.
The 14 zones today
The half-hour offsets are spread across several regions. In Asia they cover Myanmar, Nepal, India, Sri Lanka, Afghanistan and Iran; in Australia, Lord Howe Island, Broken Hill, Adelaide, Darwin and Eucla; in the Americas, St. John’s on the island of Newfoundland; and in the Pacific, Chatham Islands and Marquesas Islands. The table gives each one with the year from which its current standard time has applied without a break.
| Zone | Standard time | Unchanged since | Clock changes today |
|---|---|---|---|
| Chatham Islands | UTC+12:45 | 1946 | yes |
| Lord Howe Island | UTC+10:30 | 1981 | yes |
| Broken Hill | UTC+9:30 | 1899 | yes |
| Adelaide | UTC+9:30 | 1899 | yes |
| Darwin | UTC+9:30 | 1899 | no |
| Eucla | UTC+8:45 | 1895 | no |
| Myanmar | UTC+6:30 | 1945 | no |
| Nepal | UTC+5:45 | 1986 | no |
| India | UTC+5:30 | 1906 | no |
| Sri Lanka | UTC+5:30 | 2006 | no |
| Afghanistan | UTC+4:30 | 1945 | no |
| Iran | UTC+3:30 | 1978 | no |
| St. John’s | UTC−3:30 | 1935 | yes |
| Marquesas Islands | UTC−9:30 | 1912 | no |
Fractional standard times, east to west
The 45-minute offsets are highlighted.
Where the minutes came from
Each of these offsets has its own starting point in the record. Some go back to the first standard time the place adopted; others replaced a whole-hour offset or a different fraction much later.
- Chatham Islands: UTC+12:45 since January 1, 1946; before that, another fractional offset, UTC+12:15.
- Lord Howe Island: UTC+10:30 since March 1, 1981; before that, UTC+10.
- Broken Hill: UTC+9:30 since May 1, 1899; before that, UTC+9.
- Adelaide: UTC+9:30 since May 1, 1899; before that, UTC+9.
- Darwin: UTC+9:30 since May 1, 1899; before that, UTC+9.
- Eucla: UTC+8:45 since December 1, 1895; before that, local mean time, UTC+8:35:28.
- Myanmar: UTC+6:30 since May 3, 1945; before that, UTC+9.
- Nepal: UTC+5:45 since January 1, 1986; before that, another fractional offset, UTC+5:30.
- India: UTC+5:30 since January 1, 1906; before that, another fractional offset, UTC+5:21:10.
- Sri Lanka: UTC+5:30 since April 15, 2006; before that, UTC+6.
- Afghanistan: UTC+4:30 since January 1, 1945; before that, UTC+4.
- Iran: UTC+3:30 since November 11, 1978; before that, UTC+4.
- St. John’s: UTC−3:30 since March 30, 1935; before that, another fractional offset, UTC−3:30:52.
- Marquesas Islands: UTC−9:30 since October 1, 1912; before that, local mean time, UTC−9:18.
The three 45-minute zones
Only three zones use a 45-minute mark. Nepal has kept UTC+5:45 since 1986; before that it was on UTC+5:30. The Chatham Islands sit at UTC+12:45, exactly 45 minutes ahead of the rest of New Zealand, and move their clocks on the same days. Eucla is the third: a small area in Western Australia that keeps UTC+8:45, between Perth’s UTC+8 and Adelaide’s UTC+9:30.
Half hours and summer time
A fractional offset combines with seasonal changes in the usual way. St. John’s moves from UTC−3:30 to UTC−2:30 in summer, and Adelaide from UTC+9:30 to UTC+10:30. Lord Howe Island is the odd one out: its clocks move by only 30 minutes, from UTC+10:30 to UTC+11, so for half the year it shares a clock time with Sydney and for the other half it does not.
India’s single zone, India, has kept UTC+5:30 as standard time since 1906, and its record shows no seasonal changes since 1970. At the reference city, Kolkata, that clock runs 23 minutes behind local mean solar time. A half-hour offset is not in itself closer to the sun: at Nepal the 45-minute offset leaves the clock 4 minutes ahead of solar time, and at Marquesas Islands the clock is 12 minutes behind it.
Offsets that were given up
The list of fractional offsets used to be longer. 12 zones moved off one after 1970. Two of these moves were short experiments that were later reversed: Venezuela used UTC−4:30 from 2007 to 2016, and North Korea used UTC+8:30 from 2015 to 2018, in both cases before returning to the whole-hour offset they had left. Others were long-standing: Liberia kept a clock about 44 minutes behind UTC until 1972, and Guyana used UTC−3:45 until 1975.
| Zone | Fractional standard time used after 1970 | Standard time today |
|---|---|---|
| Venezuela | UTC−4:30, until 2016 | UTC−4 |
| Guyana | UTC−3:45, until 1975 | UTC−4 |
| Kiritimati | UTC−10:40, until 1979 | UTC+14 |
| Liberia | UTC−0:44:30, until 1972 | UTC+0 |
| Nauru | UTC+11:30, until 1979 | UTC+12 |
| Norfolk Island | UTC+11:30, until 2015 | UTC+11 |
| Suriname | UTC−3:30, until 1984 | UTC−3 |
| Pitcairn Islands | UTC−8:30, until 1998 | UTC−8 |
| North Korea | UTC+8:30, until 2018 | UTC+9 |
| Cook Islands | UTC−10:30, until 1978 | UTC−10 |
| Singapore | UTC+7:30, until 1981 | UTC+8 |
| Bhutan | UTC+5:30, until 1987 | UTC+6 |
Reading these offsets
A fractional offset is still a fixed offset: the clock is a set number of hours and minutes from UTC, and it changes only when the zone’s rules change. The converter on this site handles them like any other zone, and every result shows the full offset, minutes included, for the date chosen. The list of fractional offsets repeats the tables above with links to each record.
The counts here describe the zones in the tz database, each represented by a reference city. A zone that covers part of a country, such as Eucla, counts the same as a zone covering a whole nation, such as India.
Source: IANA Time Zone Database, release 2026f (public domain), computed by this site; see about the data for definitions. Look up any zone in the converter.