How to use this calculator
The world clock shows one current moment in several locations. Add cities or IANA time zones to compare their local times, choose a 12-hour or 24-hour display, and keep the clocks you use most often. It is useful for a quick check before contacting someone in another region or for keeping an international team’s working day in view.
Use the UTC preview field to compare locations at a specific moment instead of now. The date matters as much as the hour: one city can already be on tomorrow’s date while another is still on yesterday’s. Read the date and offset alongside every clock, particularly when planning near midnight or during weeks when different regions change clocks on different dates.
Formula and calculation method
Displayed local date and time = one shared instant interpreted using each location’s time-zone rules.
Start from the same instant
All live clocks use the current device time as their common reference. Each location formats that instant according to its own time-zone rules. The tool does not independently synchronize with an atomic clock service. Keeping the device clock correctly synchronized is therefore important when you want accurate current-time comparisons.
Use location rules instead of fixed offsets
A named zone can change its UTC offset across the year. Choosing America/New_York preserves the location’s date-dependent rules, while assuming a permanent five-hour difference from UTC does not. Abbreviations are display aids rather than globally unique identifiers; different places can use similar short names for different offsets.
Worked examples
A quarter-hour offset
At 00:00 UTC on January 15, 2024, Kathmandu is at 05:45 on the same date. Its offset includes 45 minutes, so rounding the difference to whole hours loses information. The world clock preserves these non-whole-hour differences when displaying the same instant in each selected location.
Cities on different dates
At 23:00 UTC on January 15, 2024, Tokyo is at 08:00 on January 16 while New York is at 18:00 on January 15. A message saying only eight in the morning is incomplete. Include the local date and location when turning a quick clock comparison into an appointment.
Compare winter and summer
Preview 12:00 UTC on January 15 and July 15, 2024. New York shows 07:00 in January and 08:00 in July under that year’s rules. UTC remains the same anchor while the local clock changes its relationship to it. This is why a memorized difference can fail when reused months later.
Edge cases and practical checks
Clock accuracy and browser updates
The live display inherits the device’s system time and the time-zone rules available in the browser. Government rule changes can require a browser or operating-system update before future conversions reflect them. For important travel or meeting plans far in the future, recheck the local times closer to the date.
Visual cues and saved preferences
Day or night styling is based on a broad local-hour cue, not an astronomical sunrise or sunset calculation. The clock list is a preference stored in your browser when storage is available. It does not synchronize with a personal account or imply a connection to anyone else’s calendar.
Frequently asked questions
Where does the current time come from?
The clocks use your device’s current time. They convert that one instant to the selected locations. If all clocks appear consistently early or late, check the system clock and automatic time settings before changing the selected time zones.
Can two cities have different dates at the same time?
Yes. Time zones span enough offsets that one instant can fall on different local dates. Always read the date beside the clock when coordinating across regions. A correct hour paired with the wrong date can move an appointment by a full day.
Why did the difference between two cities change?
One or both locations may have changed their seasonal offset. Different regions can transition on different dates, creating temporary differences during spring and autumn. Use a date-specific preview or the time-zone converter instead of assuming the current gap applies throughout the year.
Can I show 24-hour time?
Yes. Choose the 24-hour display setting. This changes presentation rather than the underlying instant. It can make overnight and international schedules easier to read, but you still need the date and selected location to identify a particular event unambiguously.
Is the shaded clock showing actual sunset?
No. Its appearance provides a simple cue based on the local hour. Actual sunrise and sunset depend on geography and season and are outside this tool’s calculation. Use a dedicated astronomical source when daylight availability is important to your plans.
Which tool should I use to arrange a meeting?
Use Time Zone Converter for one proposed date and time, or Meeting Planner to search several people’s working windows. The world clock is best for quick comparisons of now or a fixed UTC preview rather than finding mutual availability automatically.
Published by TrueHour. Calculation methodology and sources · Report a correction · Time and date guides