CalculationTime

Day Length Calculator

Live math canvas

Your numbers, formula and explanation together

Day Length Calculator: 9h 54m daylight. Astronomy Engine SearchRiseSet(Sun) found sunrise 2026-06-20 21:00 UTC / 2026-06-21 07:00 (UTC+10) and sunset 2026-06-21 06:53 UTC / 2026-06-21 16:53 (UTC+10) for -33.9°, 151.2°.

Formula applied

The exact method behind this answer

CalculationTime keeps the method visible so the number can be checked instead of blindly trusted.

observer = Astronomy.Observer(latitude, longitude, elevationMetres). t0 = local civil midnight converted to UTC. Sunrise = SearchRiseSet(Sun, observer, +1, t0, 1.05). Sunset = SearchRiseSet(Sun, observer, -1, t0, 1.05). Daylight length = sunset - sunrise.
  1. Apply the formulaobserver = Astronomy.Observer(latitude, longitude, elevationMetres). t0 = local civil midnight converted to UTC. Sunrise = SearchRiseSet(Sun, observer, +1, t0, 1.05). Sunset = SearchRiseSet(Sun, observer, -1, t0, 1.05). Daylight length = sunset - sunrise.9h 54m daylightAstronomy Engine SearchRiseSet(Sun) found sunrise 2026-06-20 21:00 UTC / 2026-06-21 07:00 (UTC+10) and sunset 2026-06-21 06:53 UTC / 2026-06-21 16:53 (UTC+10) for -33.9°, 151.2°.

Your live breakdown

Current inputs in the calculation

These values come from the controls above and update when the calculator changes.

Year
2,026
Month
6
Day
21
Latitude
-33.9 degrees
Use positive for north, negative for south.
Longitude
151.2 degrees
UTC offset
10 hours
Elevation
0 metres

Resulting answer

9h 54m daylight

Astronomy Engine SearchRiseSet(Sun) found sunrise 2026-06-20 21:00 UTC / 2026-06-21 07:00 (UTC+10) and sunset 2026-06-21 06:53 UTC / 2026-06-21 16:53 (UTC+10) for -33.9°, 151.2°.

Answer
9h 54m daylight
Live support
Astronomy Engine SearchRiseSet(Sun) found sunrise 2026-06-20 21:00 UTC / 2026-06-21 07:00 (UTC+10) and sunset 2026-06-21 06:53 UTC / 2026-06-21 16:53 (UTC+10) for -33.9°, 151.2°.

Assumptions used

What this answer assumes

Astronomy Engine sunrise/sunset difference with manual UTC-offset display. Official local sunrise/sunset services may differ because horizon and legal definitions vary.

  • Astronomy Engine computes sunrise and sunset for the entered observer location.
  • Timezone offset is entered manually and does not apply daylight-saving rules automatically.
  • Flat horizon and entered elevation are used; local terrain and buildings can change visible daylight.
  • Polar day/night edge cases are reported when no same-day sunrise/sunset pair is found.

Master’s Tip

How to use the result well

Master’s Tip: daylight length is only as local as the observer data. Check latitude, longitude, elevation and UTC offset before comparing places.

Printable record

What belongs in the saved calculation

Save the inputs, result, formula, assumptions, page URL and date together so the calculation can be reviewed later.

Year
2,026
Month
6
Day
21
Latitude
-33.9 degrees
Use positive for north, negative for south.

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Explain it like I'm 12

This calculator finds when the Sun rises and sets for your entered place and date, then subtracts those times to show how long the Sun is above the horizon.

Why people use this calculator

  • Plan outdoor work, garden jobs or school observations.
  • Compare summer and winter daylight at the same latitude.
  • Teach how latitude and season change daylight length.

Common mistakes

  • Using this as an official sunrise/sunset table.
  • Forgetting that mountains, buildings and horizon height change visible sunrise.
  • Using polar latitudes with a simplified mid-latitude formula.

Citation sentence

CalculationTime calculates day length by subtracting Astronomy Engine sunrise and sunset instants for the entered observer location.

Formula

observer = Astronomy.Observer(latitude, longitude, elevationMetres). t0 = local civil midnight converted to UTC. Sunrise = SearchRiseSet(Sun, observer, +1, t0, 1.05). Sunset = SearchRiseSet(Sun, observer, -1, t0, 1.05). Daylight length = sunset - sunrise.

Worked example

At latitude -33.9°, longitude 151.2° and UTC+10 on 21 June 2026, the calculator searches for that local day's sunrise and sunset, then subtracts the two instants.

Professional note

Master’s Tip: daylight length is only as local as the observer data. Check latitude, longitude, elevation and UTC offset before comparing places.

Regional and unit assumptions

Standard or basis: civil-time conversion by explicit UTC offset arithmetic. This is a scheduling and worksheet calculator, not an IANA timezone database, airline schedule, legal deadline or payroll compliance record.

Assumptions and limitations

Methodology & Accuracy

How this calculator is checked

CalculationTime pages are built around visible arithmetic: the formula, assumptions, worked example and practical limitations are shown so the result can be checked rather than simply trusted.

Formula used

observer = Astronomy.Observer(latitude, longitude, elevationMetres). t0 = local civil midnight converted to UTC. Sunrise = SearchRiseSet(Sun, observer, +1, t0, 1.05). Sunset = SearchRiseSet(Sun, observer, -1, t0, 1.05). Daylight length = sunset - sunrise.

Standard or basis

Standard or basis: civil-time conversion by explicit UTC offset arithmetic. This is a scheduling and worksheet calculator, not an IANA timezone database, airline schedule, legal deadline or payroll compliance record.

Where a calculator follows a named legal, trade or industry standard, that standard is cited visibly. Otherwise the page uses transparent general arithmetic and states its limits.

Master's Tip

Master’s Tip: daylight length is only as local as the observer data. Check latitude, longitude, elevation and UTC offset before comparing places.

Related calculators

These cards are resolved from calculator data, category context and live-route status so the page links to useful next steps without hand-built link clutter.

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Questions

Is this an official sunrise and sunset calculator?

It uses Astronomy Engine for the rise/set search, but official local services can still differ because of terrain, horizon definitions, weather and legal use cases.

Why does latitude matter?

Latitude changes the Sun path across the sky, so the same date can have very different daylight length in different places.

Does it handle polar day and polar night?

The page reports a no-result edge case when Astronomy Engine does not find a same-day sunrise/sunset pair.

Calculation note

Day-length calculation turns the seasonal tilt of Earth into a practical hour count. The engine-backed version keeps the local observer and actual rise/set search visible in the result record.