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 is the primary time standard by which the world regulates clocks. It's the successor to GMT and is based on atomic time for precision.
What is Daylight Saving Time (DST)?
DST is the practice of advancing clocks by one hour during warmer months to extend daylight into the evening.
What does GMT stand for?
GMT stands for Greenwich Mean Time, the historic time standard based on the Prime Meridian in Greenwich, London.
How many time zones are in the USA?
The USA and its territories use 9 standard time zones. The 4 contiguous US states time zones are Pacific, Mountain, Central, and Eastern.
What are leap seconds?
A leap second is a one-second adjustment added to UTC to keep it in sync with the Earth's irregular rotation.
What is the time difference between New York and London?
London is typically 5 hours ahead of New York. The exact difference can vary due to Daylight Saving Time changes.
What is the time difference between PST and EST?
Eastern Standard Time (EST) is 3 hours ahead of Pacific Standard Time (PST). For example, when it is 9 AM in PST, it is 12 PM in EST.
What are time zones?
Time zones are regions of the globe that observe a uniform standard time for legal, commercial, and social purposes. They are based on longitudinal lines.
What is the International Date Line (IDL)?
The International Date Line is an imaginary line on the surface of the Earth that runs from the north pole to the south pole and marks the change of one calendar day to the next.
How do you read a 24-hour clock?
For times after 12 PM, subtract 12 from the hour to get the PM time. For example, 14:00 is 2 PM. Morning hours (1-12) are the same as AM hours.
Date & Calendar Calculations
What is a leap year?
A leap year has 366 days instead of 365, with the extra day being February 29th. It occurs every 4 years to keep the calendar aligned with the seasons.
How do I calculate my age?
To find your exact age, subtract your birth date from the current date. Our Age Calculator can do this for you instantly, showing years, months, and days.
What are ISO week numbers?
The ISO 8601 week numbering system is an international standard for numbering weeks. A week always starts on Monday, and week 1 is the first week with a Thursday.
Website Tools & Features
How do you manage time zones for a remote team?
Use a meeting planner to find overlapping hours, set core collaboration times, and clearly communicate in UTC.
How do you schedule an international event?
Announce the event in UTC, use a meeting planner to check multiple time zones, and provide a shareable link.
How do I use an online stopwatch?
Click "Start" to begin timing, "Pause" to stop, "Lap" to record a split time without stopping, and "Reset" to clear the timer.
What is a world clock?
A world clock shows the current local time in various cities around the globe on a single dashboard, helping you track multiple time zones at once.
Moon & Astronomy
What is a supermoon?
A supermoon is a full moon or new moon that nearly coincides with perigee—the closest that the Moon comes to the Earth in its elliptic orbit—resulting in a slightly larger-than-usual apparent size.
What is an equinox?
An equinox occurs twice a year (around March 20 and September 22) when the Sun is directly above the Earth's equator. On these days, day and night are of approximately equal length everywhere on Earth.
What is a solstice?
A solstice occurs twice a year when the Sun reaches its most northerly or southerly excursion relative to the celestial equator. It marks the longest day (summer solstice) and shortest day (winter solstice) of the year.