8 free tools
Date and time calculators
Date math looks simple until months have different lengths, leap years add a day, and deadlines fall on weekends. These tools count exact ages in years, months, and days, find the number of days between two dates, add or subtract days from a date, total up time durations, and run countdowns and a stopwatch.
All date & time tools
Age Calculator
Age calculator that finds your exact age in years, months, and days, plus total weeks, total days, and a countdown to your next birthday. Free.
Countdown Timer
Free online countdown timer with hours, minutes, and seconds, one-tap presets, pause and resume, and a beep when time is up. Stays accurate in tabs.
Date Add Calculator
Date calculator to add or subtract days, weeks, months, or years from any date, with business-day mode and correct month-end handling.
Days Between Dates Calculator
Days between dates calculator: count calendar days, weeks, months, and weekdays between any two dates, with an option to include the end date.
Military Time Converter
Convert military time to standard time and back as you type, see how to say it, and use the full 24-hour military time chart. Handles 0000 and 2400.
Online Stopwatch
Online stopwatch with lap and split times, hundredths of a second, and Space/L/R keyboard shortcuts. Stays accurate in background tabs. Free.
Time Duration Calculator
Time duration calculator: find the hours and minutes between two dates and times, with decimal hours for timesheets. DST-aware and free.
Time Zone Converter
Convert time between PST, EST, UTC, London, India and any city. DST handled automatically, plus a meeting planner that shows overlapping work hours.
About these tools
Common uses: checking how many days until a trip or due date, counting a 90-day return or notice window, adding up hours on a timesheet, or working out someone's exact age for a form. From January 31, adding one month lands on February 28 or 29, not March 3, and the calculators handle those edge cases for you.
All calculations use your device's local time zone and run entirely in your browser. Nothing is sent to a server, and the tools keep working offline once the page has loaded.