Astronomical season change events over a date range.

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Overview

Returns the astronomical season change events — the beginnings of spring, summer, autumn, and winter — within a specified date range. Seasons are defined astronomically by the Sun's ecliptic longitude: 0° is the vernal equinox (spring), 90° is the summer solstice, 180° is the autumnal equinox, and 270° is the winter solstice. Note that astronomical seasons are hemisphere-dependent: spring in the northern hemisphere is autumn in the southern hemisphere.

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Request parameters

Name	Type	In	Required	Description	Example
date1	Date	Body	Yes	The start date (or single query date) for the computation. Accepted formats: YYYY-MM-DD for date-only fields, ISO 8601 datetime string (YYYY-MM-DDTHH:MM) for datetime fields.
date2	Date	Body	Yes	The end date of the query range. Must be on or after date1. Accepted format: YYYY-MM-DD. The range is inclusive of both dates.
lat	Float	Body	Yes	Observer latitude in decimal degrees. Valid range: -90.0 (South Pole) to 90.0 (North Pole). Used to compute the observer's position on Earth's surface for all sky calculations.
lon	Float	Body	Yes	Observer longitude in decimal degrees. Valid range: -180.0 to 180.0. Negative values are west of the Prime Meridian, positive values are east.
timezone_slug	Choice	Body	Optional	Slug of a timezone record used to localise event datetimes in the response (e.g. america-new-york). When omitted, the timezone is derived automatically from the supplied coordinates. Obtain valid timezone slugs from the timezone list endpoint.

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Response fields

Name	Type	Nullable	Description	Example
body	String	Yes	Skyfield key of the queried body, or null for fixed-body endpoints (sunrise, moonrise, twilight, seasons).	SUN
count	Integer	—	Number of events found within the requested date range.	30
date1	Datetime	—	Start of the query window echoed from the request.	2025-06-01T00:00:00
date2	Datetime	—	End of the query window echoed from the request.	2025-06-30T00:00:00
events	Array	—	List of discrete sky events ordered chronologically.
events[].date	String	—	Date formatted as abbreviated weekday and month (e.g. Sat Jun 21 2025).	Sat Jun 21 2025
events[].datetime	Datetime	—	Full datetime of the event in the observer's local timezone.	2025-06-21T06:14:00-07:00
events[].duration_days	Float	—	Days from this event until the next, rounded to one decimal place.	0.3
events[].duration_hours	Float	—	Hours from this event until the next, rounded to one decimal place.	8.2
events[].duration_minutes	Float	—	Minutes from this event until the next event in the sequence.	489.5
events[].duration_weeks	Float	—	Weeks from this event until the next, rounded to three decimal places.	0.048
events[].id	Integer	—	Sequential index of the event within the result set.	0
events[].literal_date	String	—	Date formatted as full month name and day (e.g. June 21).	June 21
events[].name	String	—	Human-readable label for the event type (e.g. Sunrise, Full Moon, Summer).	Sunrise
events[].naturalday	String	—	Human-relative day description (e.g. Today, Yesterday, Tomorrow).	Tomorrow
events[].naturaltime	String	—	Human-relative time description generated by Django humanize (e.g. 3 hours ago).	3 hours from now
events[].short_date	String	—	Date formatted as ISO 8601 (YYYY-MM-DD).	2025-06-21
events[].short_literal_date	String	—	Date formatted as abbreviated month name and day (e.g. Jun 21).	Jun 21
events[].symbol	String	—	Unicode symbol representing the event type (e.g. ☀ for sunrise, 🌑 for new moon).	☀
events[].time	String	—	Time of the event formatted as 12-hour clock with AM/PM (e.g. 06:14 am).	06:14 am
events[].type	Integer	—	Integer code identifying the event type within its category (0 = first variant, 1 = second, etc.).	1
lat	Float	—	Observer latitude echoed from the request.	48.428333
lon	Float	—	Observer longitude echoed from the request.	-123.364722
tz	String	—	Resolved IANA timezone name for the observer's location.	America/Vancouver