Free calendar tools
Answers for dates that matter
Fast, private and browser-based. Your dates stay on your device; no account or download is required.
Day of the Week Calculator
Enter any Gregorian date to find its weekday, day number and ISO week.
Open calculator →02Same Calendar Year Finder
Find years with exactly the same month and weekday pattern.
Open calculator →03Days Between Dates Calculator
Count calendar days, weeks and business days between two dates, with US federal holidays skipped.
Open calculator →04Exact Age Calculator
Exact age in years, months and days, the weekday you were born and the countdown to your next birthday.
Open calculator →05Day of the Year Calculator
Convert a date to its day number and YYDDD Julian code, or turn a day number back into a date.
Open calculator →Calendar math you can inspect
These tools use the Gregorian calendar, the calendar the United States has followed since 1752, and do all their math in your browser. The same tested rules power Old Calendars's year pages. Results are intended for everyday reference; always confirm court, tax, banking, medical or contract deadlines with the responsible organization.
Why results can differ between tools
“Days between” normally means elapsed midnights and excludes the start date. Business-day totals depend on which holidays and weekends an organization excludes. Week numbers may follow ISO 8601 or US conventions. We label the convention beside each result instead of presenting an unexplained number.