Days between dates, add/subtract days from a date, weekday lookup.
Three date utilities in one: exact days between two dates, add or subtract days/months/years from a date, and find the weekday of any date.
100% client-side — zero uploads, maximum privacy
Instant results — no waiting for server processing
Secure — your data never leaves your browser
Free to use — no sign-up required
Real-time calculation as you type — no submit button needed
Step-by-step breakdowns for full transparency
Amortization schedules, unit conversions, and health formulas
Bookmarkable results for quick reference
Works offline after initial page load
Calculate the number of days between two project milestones
Add or subtract days, weeks, or months from a date
Determine business days between two dates excluding weekends
Calculate deadlines for payment terms and contract durations
Find the day of the week for any historical or future date
The result is the number of full days between the dates (end − start), excluding the start day itself.
Percentage of, percentage change and percentage increase/decrease.
Monthly payment, total interest and full amortization schedule.
Length, weight, temperature, data, area, volume, time and speed conversion.
Exact age in years, months, days, plus days until your next birthday.
Convert between decimal, hex, binary and octal with ASCII view.
Body Mass Index with healthy-range guidance.