Hours of daylight

Quick answer

Why do the hours of daylight matter for waking up?

Daylight is what sets your body clock. The more the day length swings across the year, the more your natural wake time drifts with it — which is why a winter alarm in a high-latitude city is so much harder than the same alarm in summer. Pick a city to see the swing.

The seasonal swing

Longest and shortest days in a few cities, computed from the solar geometry:

City	Longest day	Shortest day
London	16h 36m (Jun)	7h 52m (Dec)
New York City	15h 04m (Jun)	9h 17m (Dec)
Los Angeles	14h 25m (Jun)	9h 54m (Dec)
Chicago	15h 12m (Jun)	9h 09m (Dec)
San Francisco	14h 46m (Jun)	9h 34m (Dec)
Toronto	15h 26m (Jun)	8h 57m (Dec)

Major cities

Thousands of cities are covered — start with the majors below; each city page links to others nearby.

United Kingdom

London

United States

Canada

Mexico

Mexico City

Brazil

Germany

The Netherlands

Amsterdam

Belgium

Brussels

Spain

Portugal

Lisbon

Italy

Switzerland

Austria

Vienna

Czechia

Prague

Poland

Warsaw

Sweden

Stockholm

Norway

Oslo

Denmark

Copenhagen

Finland

Helsinki

Ireland

Dublin

Iceland

Reykjavík

Greece

Athens

Hungary

Budapest

Romania

Bucharest

Ukraine

Kyiv

Russia

Moscow

Turkey

Istanbul

United Arab Emirates

Qatar

Doha

Saudi Arabia

Riyadh

Israel

Egypt

Cairo

Kenya

Nairobi

Nigeria

Lagos

South Africa

Morocco

Casablanca

Japan

South Korea

Seoul

China

Hong Kong

Hong Kong

Taiwan

Taipei

Singapore

Singapore

Thailand

Bangkok

Malaysia

Kuala Lumpur

Indonesia

Jakarta

Philippines

Manila

Vietnam

India

Pakistan

Bangladesh

Dhaka

Sri Lanka

Colombo

Australia

New Zealand

Auckland

Nepal

Kathmandu

Iran

Tehran

Iraq

Baghdad

Jordan

Amman

Lebanon

Beirut

Democratic Republic of the Congo

Kinshasa

Ivory Coast

Abidjan

Daylight, your body clock and your alarm

Light is the master input to the circadian system. Short winter days give it a weaker, later signal, so your clock slides and mornings arrive before any daylight does. The countermeasures are about light and timing — light exposure and sleep, fixing a drifted schedule. See also sunrise times, sunset times, time differences, and the sleep calculator.

Frequently asked questions

Why do the hours of daylight change through the year?

Because the Earth is tilted on its axis. As it orbits the sun, each hemisphere leans toward or away from the sun, lengthening or shortening the day. The effect is small near the equator and extreme near the poles, where the sun can stay up — or down — for weeks.

Where has the biggest daylight swing?

The further from the equator, the bigger the swing. High-latitude cities like Reykjavík, Stockholm and Anchorage go from nearly round-the-clock daylight in summer to just a few hours in winter, while tropical cities like Singapore barely change.

Does daylight length affect how well you sleep?

Yes — daylight is the main signal that sets your circadian rhythm. Long, bright days keep the clock well-anchored; short, dark days weaken and delay the signal, which can push your sleep later and make dark mornings much harder.

Why people use Captain Wake to wake up on time

Not because it rings louder. Because it removes every way your half-asleep brain talks you back into bed.

There is no button to tap

Swiping an alarm away is a reflex you can perform while still asleep. A mission needs your thinking brain switched on — and once it is on, sinking back under is much harder.

It survives every trick

Force-quit the app, restart the phone, flip it to silent, turn the volume down. The alarm re-arms and keeps going until the mission is actually done.

It gets you physically upright

Photo and barcode missions are anchored to a spot in another room, so the only way to stop the noise is to stand up and walk there. You cannot pre-stage it from bed.

It fixes the night, not just the morning

A sleep forecast before bed, bedtime reminders and wake-up streaks — because the 6 AM problem usually starts at 1 AM.

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