Heure d'été (DST) expliquée : Dates de changement et règles mondiales

Daylight Saving Time (DST) is the practice of advancing clocks typically by one hour during warmer spring months and resetting them back to standard winter time in autumn to extend evening daylight.

« En avant au printemps, en arrière en automne »

During the transition into DST, clocks advance by 1 hour (e.g. from 01:59:59 AM to 03:00:00 AM), effectively "losing" an hour of sleep in exchange for more evening sunlight. In autumn, clocks fall back 1 hour, repeating the hour from 01:00 to 02:00.

Quels pays appliquent l'heure d'été ?

• North America: Most of the United States (excluding Arizona and Hawaii) and Canada observe DST from the second Sunday in March to the first Sunday in November (check current New York time).
• Europe: European Union countries observe Summer Time from the last Sunday in March to the last Sunday in October (see London time and Paris time).
• Southern Hemisphere: Australia (NSW, Victoria, SA, Tasmania) and New Zealand observe DST during their summer months (October to April), shifting clocks in the opposite direction from Europe and North America (compare Sydney time and Auckland time).
• Non-Observing Nations: Most countries near the equator (such as India, Singapore, Indonesia, and Kenya), as well as China and Japan, do not observe DST because daylight hours vary little throughout the year (see Singapore time and Tokyo time).

Le décalage transatlantique de changement d'heure (Piège de planning)

One of the most frequent sources of missed business meetings and financial market confusion is the transatlantic shift discrepancy. The United States transitions into DST on the second Sunday in March and reverts on the first Sunday in November. In contrast, the European Union and the United Kingdom transition on the last Sunday in March and revert on the last Sunday in October.

As a result, for 2 to 3 weeks in March and 1 week in late autumn, the standard 5-hour time difference between New York (EDT/EST) and London (BST/GMT) shrinks to 4 hours. Global team schedulers must verify meeting times during these windows using our Global Meeting Planner or check exact dates on the Time Zone Converter.

Inversion saisonnière dans l'hémisphère sud

Because the seasons are reversed in the Southern Hemisphere, countries like Australia and New Zealand observe daylight saving during their summer (October through April). When cities in North America or Europe "spring forward" by one hour, cities like Sydney or Melbourne are preparing to "fall back" by one hour. This dual shift creates dramatic changes in time differences—for example, the time difference between New York and Sydney varies between 14 hours and 16 hours depending on the month of the year.