IconVault's DateTime Calculator handles everyday date math without a spreadsheet. Add or subtract days, weeks, months or years from any date to find deadlines and anniversaries, compute the exact difference between two dates in days, get the ISO week number and day of year for any date, and see the resulting weekday spelled out clearly.

Everything runs 100% in your browser: no sign-up, nothing uploaded, free to use. Project managers can count working days to a launch, travelers can measure trip lengths, and developers can verify ISO 8601 week numbers for reports and scheduling. Results are shown instantly as you change the inputs.