Seasons Date Calculator
Find spring, summer, autumn and winter start dates for either hemisphere. View equinoxes and solstices in your time zone and export calendar reminders.
Starts with an editable example. Replace the dates and rules with your own.
Your calculation
Ready when you are
Choose your dates.
Select your counting rules and calculate.
Calculation details
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How to use this calculator
Choose a year, hemisphere and IANA time zone. Calculate the four astronomical season starts and their elapsed lengths.
An equinox or solstice occurs at one instant worldwide. Local dates can differ across time zones; the hemisphere changes season names. Displayed times round to the nearest minute. Season length beyond December 2100 is omitted.
A worked example
The March 2026 equinox occurs around 14:46 UTC on March 20. It begins astronomical spring in the northern hemisphere and autumn in the southern hemisphere.
Are these meteorological seasons?
No. Meteorological seasons use calendar months; this calculator uses the Sun's astronomical equinoxes and solstices. Neither describes local weather.
Which calendar and years are supported?
Use Gregorian dates from 1900 through 2100, with results in that range. Daily plans allow up to 366 dates; dark-sky searches allow 31 nights. Durations, capacities and policy rules are supplied by you. Astronomy uses the bundled Astronomy Engine, sea-level geometry and browser time-zone rules. Timed exports use UTC instants; date-only events do not assign a clock time. Copy, CSV and print include calculation assumptions. Nothing is booked or scheduled outside this page.
What happens to my dates?
Calculations run on your device. Saving a calculation is optional and keeps it in this browser. A setup link contains the dates and settings you entered; anyone with the link can read them. Use one tab per saved calculator. Clear saved data from Privacy & settings.