Time & Date Frequently Asked Questions
Your guide to understanding time zones, conversions, and time-related queries. Find clear, direct, voice-optimized answers to common questions.
General Time & Time Zones
What is UTC (Coordinated Universal Time)?
UTC, or Coordinated Universal Time, is the primary time standard by which the world regulates clocks and time. It is the successor to GMT.
What does GMT stand for?
GMT stands for Greenwich Mean Time, the time zone at the Royal Observatory in Greenwich, London.
What is Daylight Saving Time (DST)?
Daylight Saving Time (DST) is the practice of advancing clocks by one hour during warmer months so that darkness falls at a later clock time.
How many time zones are in the USA?
The USA has 9 standard time zones. Including territories, the United States observes a total of 11 time zones.
What time is it in Tokyo right now?
Find the current local time in Tokyo, Japan, and see how to calculate it from your own location.
How do you convert UTC to EST?
Learn the simple steps to convert Coordinated Universal Time (UTC) to Eastern Standard Time (EST), which is UTC-5.
What is the time difference between New York and London?
London is typically 5 hours ahead of New York. This can change to 4 hours depending on Daylight Saving Time.
What is a time zone map?
A time zone map is a world map that visually displays the different standard time zones across the globe.
What is the difference between a time zone and UTC offset?
A time zone is a region (e.g., EST), while UTC offset is the time difference from UTC (e.g., -5 hours).
What is the International Date Line (IDL)?
The IDL is an imaginary line on Earth that separates one day from the next.
How many countries do not use Daylight Saving Time?
The majority of countries in the world, particularly those near the equator, do not observe DST.
What time zone is China in?
China officially uses a single time zone, China Standard Time (CST), which is UTC+8.
What is military time?
Military time is a 24-hour clock format that avoids the use of AM and PM.
Which country has the most time zones?
France has the most time zones (12), primarily due to its overseas territories.
Is Arizona on Mountain or Pacific time?
Most of Arizona does not observe DST and remains on Mountain Standard Time (MST) year-round.
What is Zulu Time?
Zulu Time is another name for UTC, often used in aviation and military contexts.
Why was time standardized?
Time was standardized in the 19th century to coordinate railway schedules and simplify global communication.
Does time pass slower in space?
Yes, due to time dilation, a phenomenon described by Einstein's theory of relativity.
Date & Calendar Calculations
How do I calculate my age from my birthdate?
To calculate your age, subtract your birth year from the current year. For more precision, account for the month and day.
How do you calculate the number of days between two dates?
To find the number of days between two dates, subtract the earlier date from the later date. Our Date Duration Calculator can do this instantly.
What are the phases of the Moon?
The Moon phases are the different ways the Moon looks from Earth over about a month. The main phases are New Moon, Full Moon, and Quarter Moons.
What week of the year is it?
The week number depends on the date and the standard used (e.g., ISO 8601). Our Week Number Calculator provides the current week number instantly.
How do you add days to a date?
To add days to a date, you can use a date calculator. Simply enter the start date and the number of days you want to add.
How does a sunrise and sunset calculator work?
It calculates sunrise and sunset times based on a location's latitude, longitude, the date, and its time zone.
What is a leap year?
A leap year is a year with an extra day (February 29th), occurring every four years to keep the calendar aligned with the Earth's orbit.
How do you calculate the day of the week for a future date?
This requires a complex algorithm like Zeller's congruence, but our date calculators handle it automatically.
What is the Gregorian calendar?
The Gregorian calendar is the most widely used civil calendar in the world today.
How long is a decade?
A decade is a period of 10 years.
How many months have 31 days?
Seven months have 31 days: January, March, May, July, August, October, and December.
What is a "blue moon"?
A blue moon is the second full moon that occurs within a single calendar month.
What is an equinox?
An equinox is one of two times a year when the Sun is directly above the equator, and day and night are of nearly equal length.
What is a solstice?
A solstice is when the Sun reaches its highest or lowest point in the sky at noon, marking the longest and shortest days of the year.
Is 2100 a leap year?
No, 2100 is not a leap year. A year divisible by 100 is not a leap year unless it is also divisible by 400.
What is a fiscal year?
A fiscal year is a one-year period that companies and governments use for financial reporting, which may not align with the calendar year.
Website Tools & Features
What is a world clock?
A world clock shows the current local time in various cities around the world on a single dashboard.
What is a countdown timer?
A countdown timer is a virtual clock that counts down from a set time to zero, often used for events, tasks, or deadlines.
How do you use a stopwatch?
To use a stopwatch, you press "Start" to begin timing, "Stop" or "Pause" to halt, and "Lap" to record split times without stopping.
How do you use a meeting planner?
To use a meeting planner, add the cities of all participants. The tool then shows a grid of corresponding times, highlighting overlapping business hours.
What is an online alarm clock?
An online alarm clock is a digital tool in your web browser that plays a sound at a specific time you set.
What is a printable calendar?
A printable calendar is a calendar that has been formatted to be easily printed on paper for offline use.
Is your World Clock accurate?
Yes, our World Clock uses official time zone databases and updates live to ensure accuracy.
Can I save my selected cities in the World Clock?
Yes, your chosen cities are saved in your browser's cookies for your next visit.
Does the Meeting Planner account for DST?
Yes, all our tools automatically adjust for Daylight Saving Time changes worldwide.
Can I calculate my age in days?
Yes, use our Age Calculator to see your exact age in years, months, and days.
Will the online alarm work if my computer is muted?
No, your computer's volume must be turned on to hear the alarm sound.
Can I add my own events to your calendar?
Currently, our calendar is for viewing and printing holidays. It does not support personal events.
Can I use the stopwatch for my workout?
Absolutely. The stopwatch includes a lap feature, making it perfect for timing workouts and splits.
What standard is the Week Number calculator based on?
It uses the ISO 8601 standard, where weeks start on a Monday, which is the international norm.
Is my data private when using your tools?
Yes. All calculations are performed in your browser. We do not store your personal data.
Do your tools work on mobile devices?
Yes, our website is fully responsive and designed to work seamlessly on phones, tablets, and desktops.
How can I request a new feature?
We'd love to hear your ideas! Please use our Contact page to send us your feature requests.
What time does the moon rise?
Moonrise and moonset times change daily. Our Moon Phases calendar focuses on the phase, not the rise/set times.
Can I convert time between three or more cities?
Yes, our Time Zone Converter and Meeting Planner tools allow you to add multiple cities for comparison.
Does the age calculator work for babies?
Yes, it is very useful for calculating an infant's age in months, weeks, and days for developmental tracking.
Why does the countdown timer sometimes jump?
To save battery, browsers slow down background tabs. When you return, our timer self-corrects to the accurate remaining time.
How do you determine which holidays to show?
We focus on official public holidays and significant national observances for each country.
Are the tools on this website free?
Yes, all the time and date tools on our website are completely free to use.