Equinoxes and solstices 2029: 20 Mar, 21 Jun, 22 Sept, 21 Dec
In 2029 the March equinox falls on 20 March at 08:01 UTC, the June solstice on 21 June at 01:48, the September equinox on 22 September at 17:38 and the December solstice on 21 December at 14:14. Each is a single instant everywhere on earth, so the local date differs by zone — east of a certain meridian these fall a day later on the calendar.
2029UTC
- March equinox Tuesday 20 March, 08:01
- June solstice Thursday 21 June, 01:48
- September equinox Saturday 22 September, 17:38
- December solstice Friday 21 December, 14:14
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Where the calendar disagrees
One instant, placed by offset — west on the left, east on the right. The date on the wall depends on where the wall is.
What each one starts, and where
| Turning point | UTC | Begins, north | Begins, south |
|---|---|---|---|
| March equinox | 20 March, 08:01 | spring | autumn |
| June solstice | 21 June, 01:48 | summer | winter |
| September equinox | 22 September, 17:38 | autumn | spring |
| December solstice | 21 December, 14:14 | winter | summer |
Where the calendar disagrees
Each of these is one instant for the whole planet, but the date on the wall depends on where the wall is. These are the places whose local date differs from the UTC one.
- March equinox — 20 March in UTC. Still the 19th in Honolulu.
- June solstice — 21 June in UTC. Still the 20th in San Francisco, New York, Toronto, Mexico City, Buenos Aires, Los Angeles and 9 more.
- September equinox — 22 September in UTC. Already the 23rd in Bangkok, Chiang Mai, Bali, Singapore, Tokyo, Sydney and 11 more.
- December solstice — 21 December in UTC. Already the 22nd in Sydney, Auckland, Canberra, Wellington.
Two definitions of the same season
Ask when summer starts and you will get two confident, different answers. The astronomical one is the solstice — the instant the sun reaches its furthest point north, which is what this page computes. The meteorological one is whole months: summer is June, July and August in the north, because climate statistics need periods of equal length that do not wander by a day and a half each year. Weather services use the second; almanacs and newspapers use the first; both are correct about different things.
The other thing worth knowing is that a solstice and an equinox are instants, not days. The June solstice does not last from midnight to midnight — it is a moment, and calling the whole day "the solstice" is a convenience. That matters here because the moment can fall either side of local midnight, which is why the same event is printed as the 20th in one country and the 21st in another, without either being a mistake.
These figures are computed rather than looked up. The solstices and equinoxes are the instants the sun's apparent longitude passes 0°, 90°, 180° and 270°, and that is calculable centuries either way. Nothing on this page is a table that could go stale — but it is checked against a second, independently written ephemeris before publication, because an unchecked calculation is just a confident one.
How to use this
- Read the UTC instant first — that is the event itself, one moment for the whole planet.
- The panel above converts it into your own time zone, where the date may be a day later.
- For the season your weather service means, use the meteorological convention: whole months, starting on the 1st.
Worth knowing: These are astronomical instants, accurate to well under a minute. They say nothing about weather: the hottest and coldest weeks lag the solstices by a month or more, and vary by how far you are from an ocean.
FAQ
When is the first day of spring in 2029?
Astronomically, the March equinox: 20 March at 08:01 UTC in the northern hemisphere. Meteorologists use a different convention — whole months, so spring begins on 1 March — and weather services around the world quote that one. Both are in use and neither is wrong; they answer different questions. In the southern hemisphere the same instant begins autumn.
Why does the equinox move between the 19th, 20th and 21st?
Because the year is not a whole number of days. Each ordinary year the equinox arrives about six hours later than the last, and each leap day pulls it back by a whole day. That four-year saw-tooth is what makes the date wander, and it is also why the Gregorian calendar skips three leap days every four centuries — without that correction the equinox would drift through the calendar.
Are day and night exactly equal at the equinox?
No, and this is the most repeated wrong fact about it. Sunrise and sunset are measured from the sun's upper edge rather than its centre, and the atmosphere refracts the image upward so the sun is visible while geometrically below the horizon. Both effects add daylight, so the equinox has several minutes more day than night everywhere. The date when they truly balance — the equilux — comes a few days earlier in spring and later in autumn, and depends on your latitude.
Is the solstice the hottest or coldest day?
No. It is the extreme of daylight, not of temperature. Land and ocean take weeks to catch up with the change in incoming sunlight, so the warmest weeks come well after the June solstice in the north and the coldest well after December — the lag is about a month inland and longer near the coast.
Where do these times come from?
They are computed from the sun's apparent longitude — the solstices and equinoxes are the instants it reaches 0°, 90°, 180° and 270° — using the method in Meeus's Astronomical Algorithms, then corrected from Terrestrial Time to UTC. Every instant on this page is checked against an independently written ephemeris before the page is published; the two agree to within a fraction of a minute.