Calculate the difference between dates or add/subtract days
Our free date calculator helps you quickly find the exact number of days, weeks, months, and years between any two dates. Whether you are planning a project timeline, counting down to an upcoming event, or verifying age for eligibility requirements, this tool delivers accurate results instantly.
The calculator offers two convenient modes. In Date Difference mode, enter a start and end date to see the total span broken down into days, weeks, months, and years. In Add/Subtract Days mode, pick a base date and specify any number of days to add or subtract -- perfect for calculating deadlines, delivery windows, or contract renewal dates.
All calculations are performed locally in your browser, so your data stays private. Results are shown in both human-readable format and ISO 8601 date format, making it easy to copy values into spreadsheets, calendars, or project management tools. Use negative numbers in Add/Subtract mode to count backwards from a given date.