Universal Date Calculator

The universal date calculator brings six of the most-used date tools together on one page, so you can switch between them without hunting for a different calculator. Pick a tab and the inputs change to match; the answer appears in the same place below every time.

The tabs are: Days Between two dates, Add / Subtract days, weeks, months, or years from a date, Business Days between two dates with weekends and public holidays removed, Age from a date of birth, a Countdown to a future date, and Day of Week for any date. Each one uses the same engine that powers its dedicated page, so the results match exactly.

This is the power-user view. If you regularly jump between counting days, checking a weekday, and working out an age, the tabbed layout saves time — enter a date, read the result, and switch tools without leaving the page. Switching tabs clears the previous result so answers from different tools are never mixed up, while the dates you typed stay put in each tab.

Everything runs in your browser: no date you enter is sent anywhere, and the calculators use real calendar lengths so leap years, month ends, and weekends are all handled correctly. Business-day counts use the national holiday list for the country you choose — the United States, the United Kingdom, or India.

To use it, choose a tab, fill in the dates or values it asks for, and press the button. For a focused single-purpose page, each tool also has its own version — for example the days between dates, age, and working days calculators — which add extra detail specific to that calculation.

Each tab uses the same calculation as its dedicated calculator: day counts subtract one UTC date from another; add or subtract shifts a date by days, weeks, months, or years; business days remove weekends and public holidays; age counts complete years, months, and days; the countdown subtracts today from a target date; and the weekday is read straight from the Gregorian calendar. All math runs in UTC for timezone safety.