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Free, instant date and time calculators. Calculate ages, find date differences, convert time zones, set countdowns, and more — no sign-up required.
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Age Calculator
Calculate your exact age in years, months, days, hours and minutes.
Date Difference
Find the exact number of days, weeks, or months between two dates.
Countdown Timer
Count down to any future event — New Year, birthday, deadline.
Time Zone Converter
Convert time across world time zones instantly.
Working Days Calculator
Calculate business days between dates, excluding weekends and holidays.
Add / Subtract Days
Add or subtract any number of days, weeks, or months from a date.
Hours From Now Calculator
Find the exact local date and time any number of hours, minutes, or days from now or ago.
Time Calculator
Add or subtract days, hours, minutes, and seconds from any clock time.
Time Duration Calculator
Calculate the hours and minutes between two times, including overnight periods.
Time Card Calculator
Total weekly work hours, unpaid breaks, overtime, and estimated gross pay.
Unix Timestamp
Convert Unix timestamps to human-readable dates and vice versa.
Week Number
Find the ISO week number for any date of the year.
Leap Year Checker
Check if any year is a leap year and when the next one is.
World Clock
See the current time in major cities around the world.
Zodiac & Chinese Sign
Find your Western zodiac sign and Chinese zodiac animal by birthday.
Day of Year
Find what day number of the year any date falls on.
Articles
Learn about dates, time, and calendars
How Many Hours Are in a Week? 168 Hours Explained
A standard week has 168 hours. See the calculation, convert weeks to hours, and understand why daylight saving can create a 167- or 169-hour local week.
What Time Will It Be in 8 Hours? Calculation Guide
Add eight hours to any starting time, handle midnight correctly, and check what local date and time it will be eight hours from now.
How Many Days Until Christmas? Count It Correctly
Calculate the number of calendar days until Christmas Day, choose inclusive or exclusive counting, and avoid time-zone and countdown mistakes.
How to Add and Subtract Time: Hours and Minutes
Learn reliable ways to add or subtract hours and minutes, carry values across 60 minutes, and handle results that cross midnight.
How Many Minutes? Convert Hours, Days, and Weeks
Convert hours, days, and weeks into minutes with simple formulas, reference values, decimal-hour examples, and elapsed-time tips.
How to Add 30 Minutes to a Time
Add 30 minutes to any clock time, including examples such as 30 minutes after 1:45 and calculations that cross an hour or midnight.
What Date Is 30 Days From Yesterday?
Thirty days from yesterday is the same as 29 days from today. Learn the rule, see a dated example, and distinguish calendar days from business days.
What Is 1640 Military Time? 4:40 PM Explained
1640 military time is 4:40 PM. See the conversion step by step, learn how to say it, and compare nearby 24-hour times.
What Is 2305 Military Time? 11:05 PM Explained
2305 military time is 11:05 PM. Learn why the leading zero in the minutes matters and how to convert late-night military time.
What Is 1940 Military Time? 7:40 PM Explained
1940 military time is 7:40 PM. Convert it correctly, read it aloud, and avoid confusing 19:40 with a duration.
What Is 1845 Military Time? 6:45 PM Explained
1845 military time is 6:45 PM. Use a simple subtraction rule and practical examples to understand this evening time.
What Is 1800 Military Time? 6:00 PM Explained
1800 military time is 6:00 PM. Learn the conversion, the correct spoken form, and the difference between 1800 and 0800.
What Is 1500 Military Time? 3:00 PM Explained
1500 military time is 3:00 PM. See why subtracting 12 works and how to convert times before and after 1500.
What Is 1400 Military Time? 2:00 PM Explained
1400 military time is 2:00 PM. Learn how to write, say, and convert this common afternoon time.
What Is 1300 Military Time? 1:00 PM Explained
1300 military time is 1:00 PM. Understand the first hour after noon and the rule for converting afternoon military time.
0000 vs 2400 Military Time: How to Write Midnight Correctly
0000 marks the start of a day, while 2400 can mark the end of one. Learn which midnight notation to use and how to avoid date errors.
How to Write Military Time Correctly: Rules, Examples, and Common Mistakes
Write military time with four digits, leading zeros, and valid minute values. Learn the rules for noon, midnight, and spoken time.
How Many Monday-to-Friday Days Are There in a Year?
Most years contain 260 to 262 Monday-to-Friday days before holidays. Learn what controls the exact total and how to calculate it.
How Many Weekend Days Are There in a Year?
A year usually has 104 weekend days, but the total can be 105 or 106. See how the starting weekday and leap years change the answer.
How Many Work Weeks Are in a Year?
A calendar year spans about 52.14 weeks, but paid work weeks depend on payroll boundaries, leave, holidays, and the employer's definition.
How Many Biweekly Pay Periods Are in a Year?
A biweekly payroll normally has 26 pay periods, with 27 in some years. Learn why the extra payday occurs and how to plan for it.
How Many Weeks Are in Half a Year?
Half a year is roughly 26 weeks, but calendar halves range from 181 to 184 days. Learn the exact answer for different meanings of half a year.
How Many Weeks Are in a Leap Year?
A leap year contains 52 weeks and 2 days. Learn how those extra days affect weekdays, ISO week numbers, payroll, and scheduling.
Milliseconds vs Microseconds vs Nanoseconds: What's the Difference?
Compare milliseconds, microseconds, and nanoseconds, convert between them, and choose the right precision for timestamps and measurements.
What Does YYYY-MM-DD Mean? The ISO Date Format Explained
YYYY-MM-DD writes the four-digit year, two-digit month, and two-digit day. Learn how to read, validate, sort, and use the format safely.
Inclusive vs Exclusive Date Counting: What's the Difference?
Inclusive counting includes one or both boundary dates; exclusive counting omits a boundary. See examples and avoid off-by-one date errors.
What Is a Julian Year? Julian Year vs Calendar Year
A Julian year is exactly 365.25 days for scientific calculations. Learn how it differs from Julian calendar and Gregorian calendar years.
Why Does a Year Have 365 Days?
The fascinating astronomy and history behind our 365-day calendar year.
How Time Zones Work: The Complete Guide
From Greenwich Mean Time to UTC offsets — everything you need to know.
The History and Rules of Leap Years
Why we add an extra day every four years, and the exceptions to the rule.
What Is Unix Time? Seconds vs Milliseconds Explained
What is a Unix timestamp, why it starts in 1970, and how to tell seconds from milliseconds.
How to Schedule Meetings Across Time Zones
Practical strategies for coordinating with remote teams around the world.
A Brief History of Calendars
From lunar calendars to the Gregorian system — humanity's quest to track time.
Daylight Saving Time: A Complete Guide
Why we change the clocks twice a year, who started it, and the ongoing debate to abolish it.
UTC vs GMT: What's the Difference?
These two terms are often used interchangeably — but they aren't quite the same thing.
Year 2038 Problem: Is the Y2K38 Bug Real?
Why some computers will run out of time on January 19, 2038, which systems are affected, and what is being done.
Why Does a Week Have Seven Days?
The ancient Babylonian and astronomical roots of our seven-day week.
How to Calculate Your Exact Age
Different methods for calculating age, and why your 'age' depends on the calendar system.
How Atomic Clocks Keep Perfect Time
The science behind the most accurate timekeeping devices ever built.
ISO 8601: The International Date Standard
Why YYYY-MM-DD is the only date format that makes sense for computers and humans.
How to Calculate Business Days
Counting working days correctly means handling weekends, holidays, and regional differences.
What Are Leap Seconds?
Occasionally we add a single second to the clock. Here's why — and why it may be abolished.
The Chinese Zodiac: A Complete Guide
The twelve animals, the sixty-year cycle, and how your birth year shapes your sign.
The Twelve Western Zodiac Signs Explained
How the constellations along the ecliptic became the basis for astrology.
Birthstones by Month: The Complete List
Discover the traditional and modern gemstone associated with every birth month.
The Pomodoro Technique: Work in Focused Bursts
How a simple kitchen timer method can transform your productivity and focus.
7 Proven Time Management Techniques
From time blocking to the Eisenhower matrix — methods that actually work.
Understanding ISO Week Numbers
How businesses and schedules use week numbers, and how to calculate them correctly.
From Sundials to Smartwatches: A History of Clocks
The 5,000-year journey of humanity's quest to measure the passing of time.
What Happened in October 1582? Why 10 Days Disappeared
How ten days vanished from October 1582, and why countries adopted the Gregorian calendar centuries apart.
How Computers Keep Time and Store Dates
Learn how computer time works, from the battery-backed real-time clock and system clock to NTP synchronization, Unix timestamps, and time zones.
Why Is Friday the 13th Considered Unlucky?
The surprising history behind one of the Western world's most enduring superstitions.
Counting Down to the New Year
Different cultures celebrate the new year on different dates — here's the fascinating variety.
Does Time Really Flow at the Same Speed?
Einstein showed that time is relative — moving clocks and gravity actually change time itself.
Lunar vs Solar Calendars: Key Differences
Why some calendars follow the moon, some the sun, and some try to track both.
What Is Epoch Time?
Understanding the reference points computers use to measure time across systems.
How to Plan Backwards From a Deadline
A practical framework for breaking big goals into dated milestones that actually get done.
The Year 2106 Problem: Unix Time's Next Overflow
The Year 2106 problem is a 32-bit Unix time overflow. Learn when it happens, how it differs from Y2038, and which systems may be affected.
Military Time Conversion: 12-Hour and 24-Hour Guide
Convert military time and 24-hour time by hand, understand 0000 vs 2400, and use practical examples for common AM and PM times.
Julian Date vs Day of Year: What Is the Difference?
Julian date, Julian day number, ordinal date, and day of year are often confused. Learn what each term means and when to use it.
How to Calculate Hours Between Two Times
Learn how to calculate hours and minutes between two times, including overnight shifts, unpaid breaks, decimal hours, and daylight saving changes.
How to Calculate Days Between Two Dates
Learn how to find the number of days between dates, choose inclusive or exclusive counting, and handle leap years, times, and workdays.
How to Add or Subtract Days From a Date
Calculate a future or past date by adding or subtracting calendar days, weeks, months, or business days without off-by-one errors.
How Many Working Days Are in a Year?
A year has about 260 weekdays before holidays. Learn the exact range, how leap years affect it, and how to calculate actual workdays.
Why Does February Have 28 Days?
February is shorter because of Roman calendar history, not astronomy alone. Learn how leap years and later calendar reforms shaped the month.
12 AM vs 12 PM: Is Midnight AM or PM?
In common usage 12 AM is midnight and 12 PM is noon, but both labels can confuse. Learn safer 12-hour and 24-hour ways to write them.
How Many Weeks Are in a Year?
A common year has 52 weeks and 1 day, while a leap year has 52 weeks and 2 days. Learn why some ISO week-numbering years have week 53.
Online Time Clock Calculator: Hours, Breaks, and Decimal Pay
Use a time clock calculator correctly, calculate paid hours after breaks, and turn hours and minutes into decimal hours for payroll.
How to Change Your Computer Date and Time Safely
Set a computer's date, time, and time zone without breaking browser certificates, scheduled tasks, or file timestamps.
Julian vs Gregorian Calendar: The Difference Explained
Compare the Julian and Gregorian calendars, their leap-year rules, and why different historical dates can appear ten days apart.
Why Is My Computer Clock Wrong? Causes and Fixes
Troubleshoot a wrong system clock, from an incorrect time zone and failed synchronization to a weak CMOS battery.
NTP Time Synchronization: How Computers Stay Accurate
Learn how Network Time Protocol checks and adjusts computer time, why clock drift happens, and when manual time changes are risky.
What Is a Real-Time Clock (RTC) in a Computer?
Understand the battery-backed clock chip that maintains date and time while a computer is powered off.
Convert Unix Timestamp to Date: A Practical Guide
Convert Unix seconds and milliseconds to a readable date, recognize the unit from its length, and avoid time-zone errors.
What Is System Time? How a Computer Tracks the Current Time
System time is the operating system's current date and time. Learn how it starts, advances, synchronizes, and differs from hardware and monotonic clocks.
How to Sync Computer Time and Fix Clock Drift
Synchronize a computer clock safely, diagnose failed time updates, and understand what automatic internet time actually changes.
BIOS Date and Time Explained: What It Controls
Learn where BIOS or UEFI date and time come from, why they reset, and how firmware time relates to the operating system clock.
Timestamp Units: Seconds vs Milliseconds vs Microseconds
Identify timestamp precision by length, convert between seconds, milliseconds, and microseconds, and avoid unit errors in APIs and databases.
How to Read ISO 8601 Dates and Times
Decode ISO 8601 dates, UTC markers, numeric offsets, fractional seconds, and week or ordinal dates using practical examples.
Date and Time Formats Explained Without Guesswork
Compare numeric dates, 12-hour and 24-hour time, ISO formats, locale display, and storage formats without introducing ambiguity.
Why Do Some Time Zones Have Half-Hour Offsets?
Learn why India, Newfoundland, Nepal, and other regions use 30- or 45-minute UTC offsets instead of whole hours.
What Is a Monotonic Clock and When Should You Use It?
A monotonic clock moves forward independently of wall-clock corrections. Learn why software uses it for durations, timeouts, and performance timing.
Calendar Week vs Workweek: What Is the Difference?
Compare ordinary calendar weeks, ISO week numbers, employer-defined workweeks, and payroll periods using clear examples.
How to Calculate Overtime Hours and Overtime Pay
Calculate weekly overtime hours and time-and-a-half pay with breaks, multiple rates, and workweek boundaries in mind.
How to Calculate Overnight Shift Hours
Calculate hours across midnight, subtract unpaid breaks, convert the result to decimal hours, and handle daylight-saving transitions.
MM/DD/YYYY vs DD/MM/YYYY: Avoid Date Confusion
Understand where month-first and day-first dates are used, why values such as 03/04/2026 are ambiguous, and how to write safer dates.
Does Unix Time Have a Time Zone? UTC Conversion Explained
Unix time represents one instant without a local time zone. Learn how offsets enter only when a timestamp is displayed or parsed.
Tools That Work Together
Each tool shows you related tools for connected tasks. Calculate an age, then check the day of the week you were born. Convert a timezone, then count down to your meeting. Everything flows naturally.
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Quick answers to common time and date questions
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