Equinox and solstice dates by year: why they move

The equinox does not keep a fixed date. In UTC, the September equinox falls on the 23rd in 2026 and on the 22nd in 2028, by the tool’s own answers. How do you get the date for your year? Type it in the equinox and solstice dates tool, which gives that year’s equinoxes and solstices to the minute.

UTC, Coordinated Universal Time, is the reference clock of time zones. A fixed rule costs a day: the March equinox falls on 20 March in UTC every year from 2026 to 2035, so “21 March” is a day late throughout.

Which years can I type in the Year field?

Without an account, the current year and the nine after it: 2026 to 2035, as of 2026. The field opens on the current year. For any other year, the tool computes nothing and says: “Only the ten years from the current one are served here: 2026 to 2035.”

Past years are outside that window too: 2025 gets the same answer as 2102.

What changes from one year to the next?

Each instant comes about six hours later than the year before, then about eighteen hours earlier in a year with a 29 February. The tool’s answers for 2026 to 2035 show it:

The seasons take about six hours more than 365 days to come round, and the calendar can only catch up by a whole day, on 29 February. That catch-up slightly overshoots, so the dates creep earlier over the decades.

That is why “21 March” fails: in the AstroPixels table for 2001 to 2100, in Greenwich Mean Time, the March equinox falls on 21 March only in 2003 and 2007.

Add a city in the tool and the date can move once more. In New York, the March equinox falls on 19 March in 2028 and 2032, the evening before the UTC date.

How do I get the dates for several years?

Type each year in turn: the tool gives one year per answer, and its calendar file holds that year’s four instants. For a year outside its window, or a century on one page, two public references do the job:

Questions

What day is the summer equinox?

There is no summer equinox: the northern summer starts at the June solstice. In UTC, the tool puts it on 21 June in most years from 2026 to 2035, and on 20 June in 2028 and 2032.

Do the solstices move too?

Yes, the same way. In UTC, the December solstice falls on 22 December in 2027, 2031 and 2035, and on 21 December in the other years from 2026 to 2035.

How many days are there between a solstice and an equinox?

About 89 to 94, and each quarter differs. For 2026, the tool’s Length of the seasons gives 92.73 days from the March equinox to the June solstice, then 93.65, 89.86 and 88.98. From 2026 to 2035, each figure moves by two hundredths of a day at most.

Sources and further reading

• AstroPixels, Solstices and Equinoxes: 2001 to 2100 — the century table in Greenwich Mean Time, where 21 March appears only in 2003 and 2007.
• US Naval Observatory, Earth’s Seasons — equinoxes, solstices, perihelion and aphelion for any year from 1700 to 2100.