Duration calculators

Duration tools answer the "how long" questions: how long between two dates, how old someone is in days, how many sleeps until a deadline, how fast a runner needs to go to finish a race in a target time. The calculations look trivial until you hit the edge cases — leap years, time zones, the awkward fact that "6 months" doesn't always mean the same number of days.

The date difference calculator reports the gap between two dates in years, months, weeks, days, hours, and minutes simultaneously. Because months and years have variable lengths, the breakdown shows both the calendar-aware decomposition (2 years, 3 months, 14 days) and the absolute total (so you can pick whichever fits the question). The age calculator applies the same arithmetic to a birthday, and the countdown to date tool runs in reverse — pick a future date, see the gap update live.

The running pace calculator covers the four interrelated quantities of a run: distance, time, pace, and speed. Type any three and the fourth fills in. Splits for common race distances (5K, 10K, half-marathon, marathon) are shown alongside. Outside the body-related tools, time-based pages here treat all dates as wall-clock local time — for cross-timezone scheduling use the dedicated timezone converter under /time/conversion/.