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Summer Solstice Calculator

The exact instant of the solstice plus the length of the longest day at your latitude, sunrise and sunset in solar time, midnight sun handled without error, and a day-by-day table showing why the Sun appears to stand still.

Related tools

All Dates & time tools →
First Day of Summer CalculatorThe exact instant summer begins — June solstice in the north, December solstice in the south — plus the latitude above which the Sun never sets and why summer is the longest astronomical season.Winter Solstice CalculatorThe exact instant of the solstice, the length of the shortest day at your latitude, polar night handled properly, and the dates of the earliest sunset and latest sunrise — which fall weeks away from the solstice itself.Anniversary CalculatorHow long has it been, exactly? Years, months and days elapsed since a wedding, a first date, a friendship or a first day at work, the total in days, weeks and hours, the countdown to the next anniversary, the milestones coming up (10 000 days, silver, gold) and — for weddings — the traditional and modern gift for that year, in both the British and the American lists.Autumnal Equinox CalculatorGet the exact instant of the autumnal equinox and of all four seasonal markers for any year, in UTC and in your own offset, with northern and southern naming and the length of each astronomical season.Birth Day of the Week CalculatorFind the weekday you were born on, the weekday of your next birthdays, which weekdays repeat most, and the Doomsday rule behind it.Daily Time Savings CalculatorSee how a few minutes saved each day compound into hours, work days and weeks over a year.Date CalculatorAdd or subtract years, months, weeks and days from any date, with a business-day mode and explicit month-end clamping.Date Pattern GeneratorList palindrome, repdigit, sequential and square-root dates over any year range, labelled per date format (DD/MM/YYYY, MM/DD/YYYY, YYYY-MM-DD).

Summer Solstice Calculator is free to use as often as you like, directly from this page. You will find it under Dates & time, with First Day of Summer Calculator and Winter Solstice Calculator for the neighbouring cases.

How to use it

  1. Open the tool — no signup or install needed.
  2. Enter your input or adjust the available options.
  3. Get your result instantly, then copy or download it.

Frequently asked questions

What does Summer Solstice Calculator do?

The exact instant of the solstice plus the length of the longest day at your latitude, sunrise and sunset in solar time, midnight sun handled without error, and a day-by-day table showing why the Sun appears to stand still.

When would I actually use this?

Answering a scheduling question exactly: how many working days until a deadline, what date falls sixty days out, and what time that is for a colleague elsewhere.

What is the most common mistake?

Counting days by subtracting dates and forgetting whether the endpoints are included. Inclusive and exclusive counts differ by one, which is the difference between meeting a deadline and missing it.

How is Summer Solstice Calculator different from First Day of Summer Calculator?

They sit next to each other but answer different questions: First Day of Summer Calculator is the one to open when you need it to the exact instant summer begins — June solstice in the north, December solstice in the south — plus the latitude above which the Sun never sets and why summer is the longest astronomical season. Pick whichever matches what you're starting from — both are free.

Is there a tool for the next step?

Winter Solstice Calculator is the closest one after this: The exact instant of the solstice, the length of the shortest day at your latitude, polar night handled properly, and the dates of the earliest sunset and latest sunrise — which fall weeks away from the solstice itself.

What else is worth having open alongside it?

Anniversary Calculator and Autumnal Equinox Calculator — they come up in the same task often enough to be worth a second tab.

Where do the figures come from?

Calendar arithmetic follows the proleptic Gregorian calendar and the IANA time-zone database, so daylight-saving transitions and leap years are handled. Public holidays vary by country and region and are not assumed.

Further reading

All guides →
ExplainerWorking Out an AnniversaryCounting back and counting forward are two different sums, and they disagree by a year on the day itself. What this calculator does with 29 February, what other date libraries do, and where the traditional and modern gift lists actually come from.ExplainerDate Arithmetic Is Harder Than It Looks"One month later" has no single correct answer, and every date library has had to pick one. Month addition is neither associative nor invertible, a day is not always 24 hours, and age is not days divided by 365.25.ExplainerLeap Years: The Rule, the Exception, and the Exception to the ExceptionDivisible by four, except centuries, except centuries divisible by four hundred. The three-line rule exists because the tropical year is not 365.25 days, and the arithmetic behind it explains ten deleted days in 1582 and a calendar that repeats exactly every 400 years.GuideThe Pomodoro Method: How Long to Work and How Long to RestTwenty-five and five come from Francesco Cirillo's method, not from a trial. What the research actually measured is task switching and the cost of getting back in — and the reason a fixed interval helps is not that 25 minutes is optimal. Plus what the planner really returns, including the long break it quietly leaves out.GuideWhat a Meeting Costs the Company, and What the Number Is ForSalary is not the cost. The ticker applies no loaded-cost multiplier of its own, so the rate box is where you have to put it. And the number is for one comparison: a recurring meeting against the written update that would replace it.ExplainerReading and Writing Military Time0800 is not “eight o'clock” and not “08:00” — it is “zero eight hundred”, with a zone letter on the end. The four digits, the spoken form, midnight at 0000, the argument about 2400, and the reason 12-hour notation cannot settle noon.