Online Alarm Clock

Calculate the time between two dates in years, months, days, weeks and hours, or add and subtract durations — with optional business days. Free, in your browser.

Find your exact age in years, months and days from a date of birth, plus total months, weeks, days and hours and a countdown to your next birthday.

Add or subtract years, months, weeks and days from any date to find the resulting date, its weekday, ISO format and how many days it is from today.

Count the working days between two dates, or add a number of business days to a start date, automatically skipping weekends.

Calculate the duration between a start and end time in hours and minutes, with totals in minutes, seconds and decimal hours, including overnight spans.

Find the best times to fall asleep or wake up based on 90-minute sleep cycles, so you wake between cycles feeling refreshed rather than groggy.