Calculate days between dates, add or subtract days, count business days, calculate your exact age. All free, in your browser.
This calculator performs all computations directly in your browser, without sending any data to our servers. It supports four modes: calculating days between two dates, adding or subtracting days from a date, counting business days (Monday–Friday), and an age calculator that shows your exact age in years, months, days, hours, and minutes.
The days-between calculation converts each date to milliseconds since the Unix epoch (January 1, 1970). The difference in milliseconds is divided by 86,400,000 (the number of milliseconds in one day) to get the exact result. This method automatically handles leap years, months with varying lengths (28, 29, 30, or 31 days), and year boundaries.
Business days are Monday through Friday, excluding Saturday and Sunday. They are essential for calculating contract deadlines, legal terms, and project planning. National holidays are not automatically excluded because they vary by country: Italy has 12 national holidays, the US has 11 federal holidays, and the UK has 8 bank holidays.
The age calculator determines your precise age in years, months, and days by counting from your birth date to today. It also shows your total age in weeks, days, and hours, a countdown to your next birthday, and your zodiac sign. It's useful for official documents, age verification, and personal curiosity.
The ISO 8601 standard defines the week numbering used across Europe and in computing systems. Weeks start on Monday, and Week 1 is the week containing the first Thursday of the year. A year can have 52 or 53 ISO weeks. This calculator automatically shows the ISO week number for every computed date.
Each date is converted to milliseconds, the difference is computed, and divided by 86,400,000 (milliseconds per day). The method is 100% accurate and accounts for leap years.
Adding days creates a new date object and increments the day by the specified number. The system automatically handles month/year boundaries, including February 29 in leap years.
Business days (or working days) are Monday through Friday, excluding Saturday and Sunday. In most countries these are the standard working days. Public holidays are not automatically excluded.
The ISO week (ISO 8601) is an international standard: weeks start on Monday and Week 1 contains the first Thursday of January. A year can have 52 or 53 weeks.
Yes, all calculations account for leap years. A year is a leap year if divisible by 4 but not by 100, unless also divisible by 400. February has 29 days in leap years.
Exact age is calculated by subtracting the birth date from today. Complete years are counted first, then remaining months, then days. The calculation accounts for varying month lengths and leap years.
Yes, use the 'Days between' mode with today as start and the future date as end. The quick-calculate buttons let you instantly find days until Christmas, New Year, and other important dates.
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