Solstice Season

A Home Assistant custom integration that provides precise astronomical season information with exact timestamps for solstices and equinoxes.

Why This Integration?

Home Assistant's built-in Season integration provides basic season information, but lacks detail. Solstice Season fills the gap by offering:

• Precise timestamps for all astronomical events (not just the current season)
• Daylight trend tracking - know whether days are getting longer or shorter
• Countdown attributes - days_until for each upcoming event
• Both calculation modes - astronomical (actual events) or meteorological (fixed dates)
• Hemisphere support - correct season mapping for both Northern and Southern hemispheres
• Multi-instance capable - track seasons for different locations

All calculations run locally using the PyEphem library - no internet connection required.

Understanding Seasons

Calculation Modes

The integration offers two ways to determine seasons:

Astronomical Mode uses the actual position of the Earth relative to the Sun. Seasons begin at the exact moment of equinoxes and solstices - these dates shift slightly each year (typically between the 19th and 23rd of the month). This is how astronomers and most of the world define seasons.

Meteorological Mode uses fixed calendar dates based on the annual temperature cycle. Seasons always start on the 1st of the month (March, June, September, December). This is commonly used by meteorologists and statisticians because it aligns with calendar months, making climate data easier to compare.

Hemispheres

The Earth's tilt means seasons are reversed between hemispheres:

Event	Northern Hemisphere	Southern Hemisphere
March Equinox	Spring begins	Autumn begins
June Solstice	Summer begins	Winter begins
September Equinox	Autumn begins	Spring begins
December Solstice	Winter begins	Summer begins

The integration handles this automatically based on the configured hemisphere setting.

Installation

HACS (Recommended)

1. Click the button above, or search for Solstice Season in HACS
2. Install the integration
3. Restart Home Assistant
4. Go to Settings → Devices & Services → Add Integration
5. Search for Solstice Season and follow the setup wizard

Manual Installation

1. Download the latest release from GitHub Releases
2. Copy the custom_components/solstice_season folder to your config/custom_components/ directory
3. Restart Home Assistant
4. Go to Settings → Devices & Services → Add Integration
5. Search for Solstice Season and follow the setup wizard

Configuration

The integration is configured entirely through the UI. No YAML required.

Option	Description	Default
Name	Instance name (used as entity prefix)	Home
Hemisphere	Northern or Southern	Auto (based on configured Home location)
Mode	Astronomical or Meteorological	Astronomical

Calculation Modes

Mode	Description
Astronomical	Based on actual equinoxes and solstices. Uses PyEphem for precise calculations. Dates vary slightly each year.
Meteorological	Based on fixed calendar dates. Northern: Spring Mar 1, Summer Jun 1, Autumn Sep 1, Winter Dec 1. Southern hemisphere is offset by 6 months.

Sensors

The integration creates 8 sensors, all grouped under a single device:

Current Season

Property	Value
Entity ID	sensor.{name}_current_season
States	spring, summer, autumn, winter
Device Class	enum
Icon	Dynamic based on season

Attributes:

Attribute	Description
mode	astronomical or meteorological
hemisphere	northern or southern
season_age	Days since the current season started

Equinox & Solstice Sensors

Four timestamp sensors showing the next occurrence of each event:

Entity ID	Event	Icon
sensor.{name}_spring_equinox	Spring Equinox	mdi:flower
sensor.{name}_summer_solstice	Summer Solstice	mdi:white-balance-sunny
sensor.{name}_autumn_equinox	Autumn Equinox	mdi:leaf
sensor.{name}_winter_solstice	Winter Solstice	mdi:snowflake

Each sensor has:

• State: ISO 8601 timestamp (UTC)
• Device Class: timestamp
• Attribute days_until: Days remaining until the event (0 on the day itself)
• Attribute last_start: Date of the most recent past occurrence (ISO date format)

After an event occurs, the sensor automatically shows the next year's date.

Note: The timestamps reflect the configured calculation mode (see Understanding Timezone Handling for details).

Next Season Change

Property	Value
Entity ID	sensor.{name}_next_season_change
Device Class	timestamp
Icon	mdi:timelapse

Shows when the next season will begin and which season it will be.

Attributes:

Attribute	Description
days_until	Days until the next season starts
event_type	spring, summer, autumn, or winter

Daylight Trend

Property	Value
Entity ID	sensor.{name}_daylight_trend
States	days_getting_longer, days_getting_shorter, solstice_today
Device Class	enum
Icon	Dynamic based on trend

This sensor indicates whether days are currently getting longer or shorter based on the position between solstices.

Next Daylight Trend Change

Property	Value
Entity ID	sensor.{name}_next_daylight_trend_change
Device Class	timestamp
Icon	mdi:sun-clock

Shows when the daylight trend will reverse (the next solstice).

Attributes:

Attribute	Description
days_until	Days until the next solstice
event_type	summer_solstice or winter_solstice

Technical Details

Property	Value
Update Interval	Once per day
IoT Class	calculated
Calculation Library	PyEphem
Platforms	Sensor

Understanding Timezone Handling

All timestamps are stored in UTC, following Home Assistant's internal design principle. Home Assistant automatically converts these to your local timezone for display in the frontend.

What This Means in Practice

Astronomical Mode:
The Spring Equinox 2026 occurs at 2026-03-20T14:46:00+00:00 (UTC). If you're in Central European Time, you'll see 15:46 (CET) or 16:46 (CEST) - this is the exact moment the event occurs at your location.

Meteorological Mode:
Season dates are stored as midnight UTC on the first day of the month. For example, meteorological spring is stored as 2026-03-01T00:00:00+00:00. In Central European Time, this displays as 01:00 (CET) or 02:00 (CEST).

Using Timestamps in Automations

When you use a timestamp sensor as an automation trigger, it fires at the stored UTC moment:

Mode	Stored (UTC)	Display (CET)	Automation triggers
Astronomical	2026-03-20T14:46:00Z	15:46	15:46 local time
Meteorological	2026-03-01T00:00:00Z	01:00	01:00 local time

This UTC-based approach ensures consistency: the same timestamp always refers to the same moment in time, regardless of timezone changes or daylight saving time transitions.

Localization

The integration supports multiple languages through Home Assistant's translation system. All sensor names and states are translated.

Currently supported languages:

• English (fallback)
• German (Deutsch)
• Dutch (Nederlands)

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

This project is licensed under the MIT License - see the LICENSE file for details.

Acknowledgments

• Inspired by the Home Assistant Season Integration
• Astronomical calculations powered by PyEphem
• Development assisted by Claude (Anthropic)