Paris
London
Madrid
Berlin
Roma
Lisboa
Moscow
Istanbul
New York
Toronto
Ciudad de México
São Paulo
Buenos Aires
Casablanca
Lagos
Cairo
Johannesburg
Dubai
Mumbai
Bangkok
Shanghai
Hong Kong
Singapore
Tokyo
Seoul
Sydney
AucklandUnderstanding time zones
A time zone is a region of the planet that applies the same legal time. The global reference is Coordinated Universal Time (UTC), heir to the Greenwich meridian: each time zone is defined by its offset from UTC, from UTC−12 to UTC+14. Metropolitan France, for example, lives at UTC+1 in winter and UTC+2 in summer, New York at UTC−5 or UTC−4, and Tokyo at UTC+9 all year round.
This converter saves you the mental arithmetic: you choose a reference city and a time, and the tool immediately shows the corresponding time in other major world cities. The side-by-side comparator lets you spot at a glance the windows when several countries are simultaneously within their office hours — the key to planning an international meeting or a family call on the other side of the world.
Daylight saving time, a classic source of mistakes
Many countries move their clocks forward one hour in spring and back one hour in autumn: this is daylight saving time (DST). The trap is that not all countries change on the same date — the United States usually switches two to three weeks before Europe — and the southern hemisphere moves in the opposite direction: when Paris moves to summer time, Sydney moves to winter time. The offset between two cities can therefore vary several times a year.
Concretely, the Paris–New York offset is 6 hours for most of the year, but temporarily slides to 5 or 7 hours during the transition weeks. This is the number-one cause of missed appointments across continents. The tool handles these changes automatically: the displayed time takes into account the daylight saving rules in force on the chosen date, city by city.
Practical use cases
Planning a meeting between Paris, New York and Tokyo becomes simple: choose a starting time and check that it falls neither in the middle of the night nor during a meal for any participant. For a long-haul flight, convert the local arrival time to anticipate the jet lag. For a call to an expatriate relative, identify their waking window before dialling. Remote workers, teams spread across continents and online event organisers save precious time — and avoid confusion between morning and evening on either side of the international date line.
Frequently asked questions about time zones
What is the difference between UTC and GMT?
GMT (Greenwich Mean Time) is the older historical reference based on astronomical observation. UTC is its modern successor, based on atomic clocks. In practice they show the same time, and offsets are now officially expressed in UTC.
Does the tool take daylight saving and winter time into account?
Yes. Each city is linked to its official time zone, including the daylight saving rules in force in the country concerned. The displayed time is therefore correct on the chosen date, even during transition periods when offsets temporarily change.
How many time zones are there in the world?
If whole-hour offsets are counted, there are 24 theoretical zones. In reality there are about 38 distinct legal times, because some countries use 30- or 45-minute offsets, such as India (UTC+5:30) or Nepal (UTC+5:45).
Why does China have only one time zone?
Although the country spans five geographic zones, China has applied a single time, UTC+8, across its entire territory since 1949. It is therefore officially the same time in Beijing and Xinjiang, more than 3,000 kilometres apart.
What is the international date line?
It is an imaginary boundary, close to the 180th meridian in the Pacific, on either side of which the date changes by one day: it is Monday to the west of the line and still Sunday to the east. It explains why some flights 'arrive before they depart' in local time.