Are these calendar days or working days?
Choose inclusive or exclusive endpoints, then exclude weekends and only the holidays supplied before calculating a target date.
Dates & time
Dates & time
Calculate calendar days, work shifts, age and fixed UTC offsets. Check date boundaries, leap days and time units with examples and stated conventions.
13 calculatorsEnglish and ChineseNo account required
From question to result
Choose a path for your question
Calculate first, understand the formula and example, then compare your options. Each link answers a different question.
How do leap days affect age and birthdays?
Use a stated anniversary convention for February 29 and distinguish completed years from the number of calendar days remaining.
Which weekday and ISO week does this date belong to?
A weekday and an ISO week-year describe different calendar properties; dates near New Year can belong to a different week-year.
How much paid time is left after breaks?
Separate elapsed duration from paid hours, explicitly allow overnight shifts, then total multiple shifts before applying a wage.
Am I converting a clock time or an absolute instant?
Fixed UTC offsets, Unix seconds and a live countdown have different inputs. Check the offset and seconds-versus-milliseconds convention.
Calculator set
Dates & time calculators
Open a calculator for an immediate estimate, then use its method notes, examples, limits, and sources to understand the result.
Days Between Dates CalculatorCount dates using calendar days rather than local-clock elapsed hours. The start date is included in work-day enumeration and the end is excluded unless the inclusive option is checked.CalculateWork Days CalculatorCount dates using calendar days rather than local-clock elapsed hours. The start date is included in work-day enumeration and the end is excluded unless the inclusive option is checked.CalculateDate From Days CalculatorAdd or subtract a whole number of calendar days, including month boundaries and leap days. A negative day count moves backward; zero deliberately returns the start date.CalculateAge CalculatorCompare a birth date with a chosen reference date using completed calendar years or days to the next birthday. February 29 anniversaries use March 1 in a non-leap year.CalculateBirthday Countdown CalculatorCompare a birth date with a chosen reference date using completed calendar years or days to the next birthday. February 29 anniversaries use March 1 in a non-leap year.CalculateDay of the Week CalculatorLook up a Gregorian calendar weekday or ISO 8601 week number. ISO weeks begin on Monday, and the first week contains January 4; the ISO week-year can differ from the calendar year.CalculateWeek Number CalculatorLook up a Gregorian calendar weekday or ISO 8601 week number. ISO weeks begin on Monday, and the first week contains January 4; the ISO week-year can differ from the calendar year.CalculateHours CalculatorCalculate a clock-time duration and subtract an unpaid break. When the end clock is earlier than the start, the overnight option adds one day; it does not add a day to equal clock times.CalculateTime Duration CalculatorMeasure the elapsed wall-clock interval between two times, without subtracting work breaks. Read hours and minutes alongside decimal hours; choose Hours Calculator for net paid shift time.CalculateTime Card CalculatorTotal shifts and break deductions from one row per shift, then apply a flat hourly rate. Use clock times rather than decimal-hour numbers in the shift rows.CalculateTime Zone ConverterConvert a clock time between explicitly entered fixed UTC offsets, including fractional-hour offsets and crossings into another day. This is not a city-time-zone or daylight-saving converter.CalculateCountdown CalculatorMeasure a fixed UTC date/time difference or start a live countdown showing days, hours, minutes and seconds. Refreshes use the current device clock, so resuming after a pause or a background tab catches up to the deadline.CalculateUnix Timestamp ConverterConvert Unix timestamps to UTC ISO dates or convert a UTC date and time to a timestamp. Choose seconds or milliseconds explicitly instead of guessing from the number’s length.Calculate
Understand, then calculate
Make sense of the key numbers in Dates & time
A calendar date and an instant are different concepts. Counting calendar days should not divide browser-local elapsed milliseconds blindly by 24 hours, because a daylight-saving transition can create a 23- or 25-hour local day. These tools construct calendar-only values at UTC midnight to retain whole-day arithmetic, or explicitly accept a fixed UTC offset for a clock conversion. A Unix timestamp instead identifies elapsed time from an epoch; seconds and milliseconds differ by a factor of one thousand.
Boundary conventions must be chosen before interpreting a count. Excluding the end date gives zero days for equal endpoints; including it counts one calendar date. Work-day calculations remove weekends and only the holidays actually supplied. An ISO week-year can differ from the calendar year near New Year, and a February 29 birthday requires a stated non-leap-year anniversary rule. A shift crossing midnight needs an explicit overnight interpretation; it should not silently become a negative paid duration. These conventions make examples reproducible without claiming legal or payroll rules.
What you can work out here
Identify the decision first, then open the calculator that answers it.
- Days Between Dates Calculator
- Count dates using calendar days rather than local-clock elapsed hours. The start date is included in work-day enumeration and the end is excluded unless the inclusive option is checked.
- Work Days Calculator
- Count dates using calendar days rather than local-clock elapsed hours. The start date is included in work-day enumeration and the end is excluded unless the inclusive option is checked.
- Date From Days Calculator
- Add or subtract a whole number of calendar days, including month boundaries and leap days. A negative day count moves backward; zero deliberately returns the start date.
- Age Calculator
- Compare a birth date with a chosen reference date using completed calendar years or days to the next birthday. February 29 anniversaries use March 1 in a non-leap year.
Core terms in plain language
Understand the recurring inputs and results instead of reading only the final number.
- Calendar date
- A year, month and day rather than an absolute clock instant.
- Inclusive endpoint
- Whether the last date is counted in the date interval.
- UTC offset
- A fixed difference from UTC; it does not infer geographic daylight-saving rules.
- Unix timestamp
- Elapsed seconds or milliseconds from the epoch, with the unit explicitly selected.
Choose with context
Which calculator should you use?
Use these distinctions to move through the Dates & time tools without comparing unrelated results.
- 01
Use calendar days or working days according to the question, explicitly choosing the endpoint convention.
- 02
Use duration for elapsed time, hours for one shift after breaks, and a time card for multiple shifts.
- 03
Use a fixed UTC offset for clock conversion or a Unix timestamp for an instant; check leap days and ISO week-years separately.
Check the stated input format, calculation convention and limits before using the result.
Common questions
What else to know about Dates & time
These answers explain how to use the estimates and where their limits begin.
How do I choose a tool?
Use calendar days or working days according to the question, explicitly choosing the endpoint convention. Use duration for elapsed time, hours for one shift after breaks, and a time card for multiple shifts. Use a fixed UTC offset for clock conversion or a Unix timestamp for an instant; check leap days and ISO week-years separately.
Are local holidays and daylight-saving rules automatic?
Work days exclude weekends and only the holidays you enter. Calendar arithmetic uses UTC dates; the time-zone converter uses fixed offsets rather than a geographic daylight-saving database. Check the actual local calendar separately.