Date & Time
Age Calculator
Exact age in years, months and days from a date of birth, with the next birthday countdown.
Count whole years, then months, then rema…
Also called how old am i · date of birth calculator
Date & Time · 18 calculators
Date & Time Calculators
Age, days between dates, adding days, day of the week, business days, time differences, time zones and Unix timestamps.
Date & Time
Date Difference Calculator
Time between two dates in years, months, days, weeks and working days.
difference = end date − start date
Also called time between dates · date duration calculator
Date & Time
Days Between Dates Calculator
Exact number of days between two dates, with and without the end date included.
days = |end date − start date|
Also called how many days between · day counter
Date & Time
Add or Subtract Days Calculator
Find the date a number of days, weeks, months or years before or after a given date.
result = start date ± the period given
Also called date plus days · add days to date
Date & Time
Birthday Countdown Calculator
Days until your next birthday, the age you will turn and what day it falls on.
days = next birthday − today
Also called days until my birthday · birthday counter
Date & Time
Day of the Week Calculator
What day of the week any date falls on, past or future, with the week number.
Derived from the proleptic Gregorian cale…
Also called what day was i born · day of week for date
Date & Time
Week Number Calculator
ISO-8601 week number for a date, and the dates a given week covers.
ISO-8601: week 1 contains the first Thurs…
Also called iso week calculator · what week is it
Date & Time
Business Days Calculator
Working days between two dates, excluding weekends and public holidays.
working days = calendar days − weekend da…
Also called working days calculator · weekdays between dates
Date & Time
Work Hours Calculator
Hours worked between a start and end time minus unpaid breaks — handles overnight shifts — with decimal hours and pay.
Hours = end − start − break (add 24 h if …
Also called hours worked calculator · working hours calculator
Date & Time
Time Difference Calculator
Hours and minutes between two times, handling shifts that run past midnight.
duration = end − start (+24 h if it cross…
Also called hours between times · time duration calculator
Date & Time
Countdown Calculator
Time remaining until any date and time, broken into days, hours and minutes.
remaining = target date and time − now
Also called days until · countdown timer calculator
Date & Time
Time Duration Calculator
Add or subtract hours, minutes and seconds, and convert the total between units.
Convert both to seconds, combine, then co…
Also called add time calculator · subtract time
Date & Time
Hours to Minutes Converter
Convert hours to minutes, seconds and days, including decimal hours.
minutes = hours × 60
Also called hours in minutes · convert hours to minutes
Date & Time
Minutes to Hours Converter
Convert minutes to hours in both decimal and hours-and-minutes form.
hours = minutes ÷ 60
Also called minutes in hours · convert minutes to hours
Date & Time
Decimal Time Converter
Convert between clock time and decimal hours for timesheets and billing.
decimal hours = hours + minutes ÷ 60
Also called decimal hours converter · time to decimal
Date & Time
Time Zone Converter
Convert a time between two UTC offsets, with the date change if it crosses midnight.
converted time = original time + (target …
Also called timezone calculator · utc offset converter
Date & Time
Unix Timestamp Converter
Convert between Unix timestamps and human-readable dates, in seconds or milliseconds.
timestamp = milliseconds since 1970-01-01…
Also called epoch converter · timestamp to date
Date & Time
Leap Year Calculator
Whether a year is a leap year, with the next ones and the rule explained.
leap = (year % 4 = 0 and year % 100 ≠ 0) …
Also called is it a leap year · leap year checker
Key date & time formulas
| Age | Count whole years, then months, then remaining days |
|---|---|
| Date Difference | difference = end date − start date |
| Days Between Dates | days = |end date − start date| |
| Add or Subtract Days | result = start date ± the period given |
| Birthday Countdown | days = next birthday − today |
| Day of the Week | Derived from the proleptic Gregorian calendar |
| Week Number | ISO-8601: week 1 contains the first Thursday of the year |
| Business Days | working days = calendar days − weekend days − holidays |
| Work Hours | Hours = end − start − break (add 24 h if overnight) |
| Time Difference | duration = end − start (+24 h if it crosses midnight) − breaks |
Date & Time questions
How is age calculated exactly?
By counting completed years since birth, then completed months, then leftover days — not by dividing total days by 365.
What is the year 2038 problem?
A signed 32-bit timestamp overflows on 19 January 2038. Modern systems use 64-bit values and are unaffected.