冬至那天 · Shortest Day

In New Zealand the sun is in the north. The building that takes your winter sun is the one on the north side.

Two facts do most of the work here, and both of them arrive backwards from the northern hemisphere. The sun is in the north — all day, every day, everywhere south of the tropics. And on the shortest day it barely gets off the ground: 30° at noon in Auckland, against 77° in December.

At 30° every metre of anything throws 1.75 m of shadow at the brightest moment of the day. An ordinary 1.8 m boundary fence three metres away stands 31° up — higher than the midwinter sun ever gets in Auckland — so it takes the whole morning, in the part of the year the sun is worth the most. The two-storey house further back is often the cheaper neighbour.

Nothing here is a legal test. Recession planes, the residential standards and what a consent will and will not allow are somebody else's document, with their own definitions and their own datum. This is the sun, the geometry and the hours.

The site

2 h 4 min of sun, 7 h 34 min behind something

The sun is up for 9 h 38 min on 2026-06-21, and 7 h 34 min of that is behind something. Times are NZST, which is the clock on the wall that day.

At noon the sun is 30° up and due north

Below the tropics in the southern hemisphere the sun is in the north all day, every day of the year. Every rule of thumb about the sunny side of a street, or which fence shades the garden, arrives here from the other hemisphere and arrives backwards: the building that takes your winter sun is the one on the north side, and a south-facing wall gets no midwinter sun at all.

A two-metre fence lays 3.5 m of shade at the brightest moment of the day

Shadow length is height divided by the tangent of the sun's altitude, so at 30° every metre of anything casts 1.75 m — and that is at solar noon (12:23), when it is shortest. An hour either side it is longer, and the whole pattern swings through the day.

“the boundary fence” costs 5 h 24 min of it

It stands 1.8 m up and 3 m away, which is 31° of sky north of here, and it spans 147° across. A metre off the top would give back 2 h 38 min.

2 h 4 min on the shortest day, 14 h 40 min on the longest

The shortest day is 2026-06-21 and the longest is 2026-12-21, and this site is a different site on each of them: the noon sun goes from 30° to 77°. An average of the two would describe a day that does not happen, which is why this page will not give you a yearly figure — every number on it is stamped with its date.

If those bearings came off a phone, they are about 23° out

A compass points at magnetic north, and in New Zealand magnetic north is roughly 20° to 25° east of true north — nearer the smaller number up north, nearer the larger down south. This page wants true bearings and it will not convert for you: the correction depends on where you are standing and on the year, and a conversion five degrees out is worse than none. A property title, a survey plan or an aerial photo already has true north on it.

2026-06-21 — sun up 9 h 38 min, 7:34 to 17:12

2 h 4 min of sun7 h 34 min behind something
15°30°45°60°75°90°ENENNWW810121416noon 12:23 · 30°
sun you getsun behind somethingwhat is in the wayshortest day, 6-21longest day, 12-21
WhatHeightAwayBearingWideIn the sky
the two-storey next door6.0 m11 m350° north14 m29° up, 65° across
the boundary fence1.8 m3 m20° north20 m31° up, 147° across

When it goes

What it does not know

It is flat ground and clear air. A hill behind the neighbours, a dip in the section and a bank across the road all change the answer and none of them is here. So does the weather: this is the sun's geometry, not how many of those hours are actually sunny, and in a Wellington winter those are very different numbers.

Each thing is a flat wall, square-on to you. That fits a fence, a boundary wall and the face of the house next door. It does not fit a building at an angle, an L-shaped block, or a tree — which is a sieve rather than a wall. A long wall running past at an angle is better entered as two or three pieces than as one.

Bearings are true, not magnetic. A phone compass is about 23° out in New Zealand, and 23° at six metres is two and a half metres of building in the wrong place. This page will not convert for you — the correction depends on where you are and on the year — but a property title, a survey plan or an aerial photo already has true north on it.

Sunrise is the standard one. The upper edge of the sun with average refraction, which is the definition every published table uses, and lands within a minute or two of them. It is not the moment your particular horizon clears. It also means the equinox comes out about ten minutes longer than its name claims, which is correct.

It answers about one date. Deliberately. The shortest and longest days at the same address differ by a factor of two in noon altitude and by six hours of daylight, so a yearly average describes a day that never happens. Every figure here is stamped with the date it belongs to.

It is not a planning test. Recession planes, height in relation to boundary, and what a consent allows are legal instruments with their own definitions. Nothing here is one of them, and nothing here has an opinion about whether a building should have been consented.