日付 & 時間
年齢、日付間の日数、労働時間などの時間計算。
6種類の計算機
日付 & 時間
Age Calculator
Your age is more than a number on a birth certificate — it's the exact span of years, months and days since you were born, and knowing it precisely matters for official forms, age limits and milestone planning. Enter your date of birth and this calculator instantly works out your calendar age, broken down into years, months and days, plus the total number of days you've lived. Leap years and whether your birthday has already happened this year are accounted for automatically, so the result is always exact.
Days Between Dates Calculator
Enter a start and end date to see exactly how many days and weeks lie between them — useful for a deadline, contract duration or countdown date.
Add to Date Calculator
Want to know what date it will be in 30 days, 6 weeks or 3 months? Enter your start date, the amount and the unit, and the calculator adds it up exactly according to the calendar, including leap years and months of different lengths.
Working Days Calculator
For project planning or a delivery deadline, often only working days count. Enter a start and end date to see the number of Monday-to-Friday days.
Months Between Dates Calculator
Unlike a simple day count, this expresses the duration between two dates as full months plus the remaining days — exactly how a rental or contract period is usually described.
Time Unit Converter
How many seconds are in a day, how many weeks in a month or how many minutes in a year? Convert any time unit exactly, from milliseconds to years. Months and years use their average length, so weeks and months always line up.
Calculating with dates and time is surprisingly tricky: leap years, varying month lengths and working days turn a simple question complex. This category offers tools that do it flawlessly for you.
Calculate your age to the day, the number of days between two dates, working days to a deadline, or convert time units from seconds to years.
Overview
The date & time category includes an age calculator, days-between-dates, working days, months-between-dates and a time-unit converter.
How to use these calculators
- 1Pick the date or time tool you need.
- 2Select the dates or enter the time value.
- 3Read the result, including any note about leap years.
Common mistakes
- Assuming every month has 30 days or 4 weeks.
- Ignoring leap years over long periods.
- Being inconsistent about counting the start and end date.
Tips
- Use working days (not calendar days) for business deadlines.
- For averages: 1 year = 365.2425 days.
よくある質問
How many seconds are in a day?
86,400 seconds (24 × 60 × 60). Convert other time units with the time-unit converter.
Do weekends count as working days?
No, the working-days calculator skips Saturday and Sunday.
Do the tools account for leap years?
Yes, all date calculations use the real calendar including leap years.