The formula
How it works
Convert a time from one zone to another using their UTC offsets. Enter the time and the two offsets, and the calculator shows the local time in the target zone and whether it lands on the previous or next day.
FAQ
What is a UTC offset?
It is how many hours a zone is ahead of or behind Coordinated Universal Time. New York is UTC−5 in winter, London is UTC+0, and India is UTC+5.5. Enter offsets as numbers, using .5 for half-hour zones like India or Newfoundland.
Does it account for daylight saving?
Not automatically — you enter the offsets yourself, so use the offset that is in effect on the date you care about. Many places shift by an hour in summer, so check whether daylight saving applies before entering the numbers.
How do I find a city’s UTC offset?
Search “[city name] UTC offset” or check a world clock site — remember to use the offset for the date in question, since it can change with daylight saving.
Can I convert between two zones that are both ahead of UTC?
Yes — enter both offsets as positive numbers, and the calculator works out the difference between them the same way it does for negative offsets.
What does the “day” result mean?
It tells you whether the converted time falls on the same calendar day as the source time, or on the previous or next day, which matters when a time difference pushes past midnight.
How many time zones are there in the world?
There are roughly 24 standard one-hour zones, plus several half-hour and even 45-minute offsets, so more than 24 distinct UTC offsets are in use globally.
Why do some countries use half-hour offsets?
A handful of countries, including India and Iran, chose offsets like UTC+5.5 to better align local clocks with solar noon rather than adopting a full-hour zone.
About the time zone calculator
This calculator converts a clock time from one time zone to another using the UTC offset of each. Time zones are defined by how far they sit ahead of or behind Coordinated Universal Time, so converting between them is a matter of adding the difference in offsets. The calculator does that and, crucially, tells you when the result rolls over into the previous or next day.
How to use it
Enter the time in the source zone, then that zone’s UTC offset and the offset of the zone you are converting to. The calculator shows the local time in the target zone. For example, 14:00 in New York (UTC−5) is 20:00 in Central Europe (UTC+1), a difference of six hours. Half-hour zones are supported by entering offsets like 5.5.
The formula
The converted time is the original plus the difference in offsets, . The time is handled in minutes from midnight; if the result goes below zero or past 24 hours, a day is subtracted or added and the calculator notes the day change. So a six-hour jump from 20:00 would land at 02:00 the following day.
Where it is used
People use it to schedule calls and meetings across countries, to catch a live broadcast or match at the right local time, and to work out when a message will reach someone abroad. Remote teams, travellers and anyone with friends or family overseas rely on it to avoid the classic mistake of calling in the middle of the night. Getting the day change right is often the whole point.