First Day of Summer

Welcome to the First Day of Summer calculator. Find the exact date and time of the summer solstice — the astronomical start of summer and the longest day of the year — for any year between 2000 and 2038. This tool includes a live countdown, complete seasonal timeline, daylight hours by latitude, multi-year comparison, and in-depth astronomical explanations. It supports both Northern Hemisphere (June solstice) and Southern Hemisphere (December solstice) calculations.

What Is the Summer Solstice?

The summer solstice (from Latin sol meaning "sun" and sistere meaning "to stand still") is the astronomical moment when the Sun reaches its highest point in the sky for the year. Earth's axial tilt of approximately 23.44° is maximally inclined toward the Sun, resulting in the longest period of daylight and the shortest night of the year.

For a few days around the solstice, the Sun appears to rise and set at nearly the same points on the horizon, and its noon altitude barely changes — hence the ancient term "sun standing still." This moment marks the peak of solar energy reaching the hemisphere and the official beginning of astronomical summer.

When Is the First Day of Summer?

The first day of summer (summer solstice) typically falls between June 20–22 (Northern Hemisphere) or December 20–23 (Southern Hemisphere). The exact date varies each year because Earth's orbital period is approximately 365.2422 days — not a perfect 365. This fractional difference, corrected by leap years, causes the solstice to shift by roughly 6 hours each year, then snap back during leap years.

Why the Date Changes

• Orbital fraction: Each year the solstice drifts later by about 5 hours 49 minutes relative to the calendar.
• Leap year correction: Adding February 29 shifts the solstice earlier by about 18 hours, keeping it anchored to June 20–22.
• Planetary perturbations: Gravitational pull from the Moon, Jupiter, and Venus create minor variations of a few minutes.

Daylight Hours on the Summer Solstice

The summer solstice is famous for being the longest day of the year. How long the day actually lasts depends entirely on your latitude — the further from the equator, the more extreme the difference:

Astronomical Summer vs. Meteorological Summer

There are two ways to define the start of summer:

Meteorological seasons are preferred for climate statistics because they align better with temperature patterns and simplify data comparison. Astronomical seasons, however, are rooted in precise celestial mechanics and are used in this calculator.

Northern vs. Southern Hemisphere

The same astronomical event is experienced differently by each hemisphere:

How to Use This Calculator

1. Select a year: Choose any year from 2000 to 2038 using the dropdown or the quick-access buttons.
2. Choose hemisphere: Northern Hemisphere uses the June solstice; Southern uses the December solstice as the start of summer.
3. View results: See the exact date, UTC time, live countdown (for future solstices), all four seasonal markers, summer duration, daylight hours by latitude, and a 5-year comparison.

Understanding Your Results

Live Countdown

For upcoming solstices, a real-time countdown shows days, hours, minutes, and seconds remaining until the exact moment of the summer solstice.

All Four Seasons

The seasonal timeline displays the year's four astronomical events (two equinoxes and two solstices), labeled appropriately for your chosen hemisphere. The summer solstice is highlighted for easy identification.

Daylight Hours by Latitude

A unique visual bar chart shows how many hours of daylight different latitudes receive on the summer solstice. This helps you understand why summer days feel so different depending on where you live.

Season Duration

Summer's duration — from the summer solstice to the autumnal equinox — varies between hemispheres. Northern summer lasts about 93–94 days, while southern summer lasts approximately 89–90 days, because Earth moves faster in its orbit during January (perihelion) than July (aphelion).

Multi-Year Comparison

The 5-year table shows how the solstice date and time shift across years, making it easy to spot the leap-year pattern and plan ahead.

Summer Traditions Around the World

Frequently Asked Questions

When is the first day of summer?

The first day of summer (summer solstice) occurs in June for the Northern Hemisphere (typically June 20–22) and in December for the Southern Hemisphere (typically December 20–23). The exact date and time vary each year because Earth's orbital period is approximately 365.2422 days. In 2026, the Northern Hemisphere summer solstice falls on June 21 at 08:24 UTC.

What happens during the summer solstice?

During the summer solstice, the Sun reaches its highest point in the sky and the day has the most daylight hours of the year. Earth's axial tilt is maximally inclined toward the Sun. After the solstice, days gradually become shorter as the hemisphere begins tilting away from the Sun.

Why does the first day of summer change each year?

The first day of summer varies because Earth's orbital period is approximately 365.2422 days, not exactly 365 days. This fractional difference, combined with the leap year cycle, causes the solstice to shift by about 6 hours each year, then jump back when a leap year adds an extra day. Gravitational perturbations from the Moon and other planets also create slight variations.

How long does summer last?

Astronomical summer (from the summer solstice to the autumnal equinox) lasts approximately 93–94 days in the Northern Hemisphere. In the Southern Hemisphere, summer (December solstice to March equinox) lasts approximately 89–90 days. The difference occurs because Earth moves faster in its orbit during January than July.

What is the difference between astronomical summer and meteorological summer?

Astronomical summer begins at the summer solstice (around June 21 in the Northern Hemisphere) and is based on Earth's axial tilt relative to the Sun. Meteorological summer always starts on June 1 and is based on the annual temperature cycle, dividing the year into four 3-month seasons. Meteorological seasons are preferred for weather forecasting and climate statistics.

How many hours of daylight are there on the summer solstice?

Daylight hours on the summer solstice depend on latitude. At the equator, there are about 12 hours 7 minutes. At 40° latitude (New York, Madrid, Beijing), approximately 15 hours 1 minute. At 50° (London, Paris), about 16 hours 21 minutes. At 60° (Helsinki, St. Petersburg), about 18 hours 52 minutes. Above the Arctic Circle (66.5°), the sun does not set at all — 24 hours of continuous daylight known as the midnight sun.

Additional Resources

• Summer Solstice — Wikipedia
• Midnight Sun — Wikipedia
• Seasons — Wikipedia