Introduction
The World Clock Calculator shows you the time in many cities at once. Pick a city, and you see its clock, its date, and how far ahead or behind it is from your home city.
You can add up to 20 clocks. Search by city, country, time zone name, or short code like IST or UTC+5:30. Each clock gets a 24-hour timeline. All timelines line up, so the same column is the same moment everywhere.
Setting up a meeting? Turn on the working-hours overlay. The tool marks the hours that work for every city with a green outline and a star. It also warns you when a city is about to start or end daylight saving time, so you don't book a call an hour off.
You can also change the date to plan ahead, switch between 12-hour and 24-hour clocks, and highlight weekends. A step-by-step section shows the math: your local time to UTC, then UTC to each city. A bar chart shows each city's offset from home in hours. For a focused two-city conversion, try the Time Zone Calculator or the Time Zone Difference Calculator.
How to use our World Clock Calculator
Pick a date, add the cities you care about, and set your work hours. The tool shows the local time and date in each city, marks the best meeting window, and shows the step-by-step math.
Viewing date: Choose the day you want to see. Use the arrows to move one day back or forward, or click "Today" to jump back to now. To shift a date by a set number of days, use the Date Calculator or the Add Days Calculator.
Quick jump (5 days): Tap a day button to switch to that date fast.
Add a location: Type a city, country, time zone, or code like NY, IST, or UTC+5:30. Click a result to add a clock card.
Number of clocks (1–20): Type how many clock cards you want. A higher number adds UTC cards. A lower number removes cards from the bottom.
Clock format: Pick 12h, 24h, or MX. MX shows 12-hour time on cards and 24-hour time on the timeline tiles. If you work in 24-hour notation, the Military Time Calculator and Time Converter Calculator help with conversions.
Primary display on cards: Choose Time to make the clock big, or Date to make the calendar day big.
Working-hours overlay: Turn this on to shade hours outside the work day. Set the Start and End hours. The end must be later than the start. For totalling a shift or a week, see the Work Hours Calculator and the Shift Calculator.
Highlight weekends: Turn this on to mark Saturday and Sunday tiles with a red border. To count only weekdays between two dates, use the Business Days Calculator.
Show zone abbreviation: Turn this on to print codes like EST or JST on each timeline tile.
Selected time range: Pick a start hour and an end hour to focus on one window. You can also drag across any timeline. Click "Clear range" to remove it. To measure the length of a window in hours and minutes, try the Time Duration Calculator.
Card buttons: Use the drop-down to change a card's time zone, the house button to set your home city, the arrows or drag handle to reorder cards, and the trash button to delete one.
Calculate and Reset: Click Calculate to refresh all clocks and results. Click Reset to go back to the default cities and settings.
What Is a World Clock?
A world clock shows the current time in many cities at once. Every city sits in a time zone, and each zone reads the clock a little differently. When it is 3:00 PM in New York, it is 8:00 PM in London and 4:30 AM the next day in Tokyo. It is the same moment in time — only the clock face changes.
How Time Zones Work
Time zones are measured from UTC (Coordinated Universal Time), the world's time standard. Each zone has an offset, like UTC−5 or UTC+9. That number tells you how many hours to add or subtract from UTC to get the local time.
- Plus (+) means the city is ahead of UTC, mostly east of the UK.
- Minus (−) means the city is behind UTC, mostly west of the UK.
- Some zones use half or quarter hours, like India (UTC+5:30), Nepal (UTC+5:45), and Newfoundland (UTC−3:30).
Converting Time Between Cities
The math is simple. First turn the local time into UTC, then add the other city's offset:
- Take the start time and subtract its UTC offset. Now you have UTC.
- Add the target city's UTC offset. Now you have the local time there.
- If the answer goes past midnight or below zero, move the date forward or back one day.
You can also just use the difference between the two offsets. Tokyo (UTC+9) minus New York (UTC−5) is 14 hours, so Tokyo is always 14 hours ahead — until daylight saving changes it. To add or subtract those hours from a clock time, the Add Hours Calculator and Subtract Time Calculator do the arithmetic for you, and the Time Difference Calculator handles gaps that cross midnight.
Daylight Saving Time (DST)
Many places move their clocks forward one hour in spring and back one hour in fall. This changes their UTC offset for part of the year. That is why New York is EST (UTC−5) in winter and EDT (UTC−4) in summer. Not every country does this. Japan, India, and most of Africa keep the same time all year, and the southern half of the world switches in opposite months. Because of DST, the gap between two cities is not always the same number of hours, so it helps to check the exact date.
Date Lines and Day Changes
Since the day is only 24 hours long, some cities are already on tomorrow while others are still on yesterday. Places near the International Date Line in the Pacific show this best: Apia in Samoa and Pago Pago in American Samoa are close neighbors but sit about a day apart on the calendar. Always check the date, not just the time, when you set a call or a deadline. The Day of the Week Calculator and the Date Duration Calculator are handy when a day shift changes your plan.
Finding a Good Meeting Time
When people work in different zones, you look for hours that fall inside everyone's workday, usually 9:00 AM to 5:00 PM local time. Those shared hours are the overlap. The wider apart the zones are, the smaller the overlap gets. Zones more than about 11 hours apart often have no overlap at all, so someone has to take an early or late call. Weekends matter too — Friday afternoon in Los Angeles is already Saturday in Sydney. If travel is part of the plan, pair this tool with the Flight Time Calculator and the ETA Calculator.
Why It Matters
Time zones affect remote work, video calls, flights, live sports, market open and close times, server logs, and family calls overseas. Getting the offset wrong by one hour, or the date wrong by one day, is one of the most common scheduling mistakes. Writing times with the zone name or UTC offset, such as "2:00 PM EST (19:00 UTC)," clears up almost all confusion. For project dates and cross-border logging, the Deadline Calculator, the Days Until Calculator, and the Julian Date Calculator round out your toolkit, while distributed teams tracking hours often reach for the Time Card Calculator.