The sun and the clock in Hanoi (2026)
Hanoi lies at 105.9°E. Its time zone, UTC+7, is built around the 105°E meridian. The two very nearly coincide: solar noon — the moment the sun is highest — falls at about 11:57, which is as close to true solar time as a zone this wide can get. The zone holds UTC+7 all year — there is no daylight saving here.
The longest day of 2026 is 22 June, with 13h 25m of daylight. The shortest is 22 December, with 10h 51m. The swing between them is 2h 34m. Inside the tropics the day length stays within a narrow band all year.
The earliest sunrise and the latest sunset do not land on the longest day. In Hanoi the sun comes up earliest on 7 June at 05:14, while the latest sunset waits until 6 July at 18:42. The equation of time is what separates them: the Earth's elliptical orbit and axial tilt move solar noon back and forth by several minutes over the year.
The sky stays usably light for a while after the sun goes down. In Hanoi that civil twilight runs about 22 minutes at the equinox.
Every figure in this section is computed from the city's own latitude, longitude and IANA time zone using NOAA solar algorithms (Spencer, 1971), accurate to about ±2 arcminutes below 65° latitude.
