Calculation guide

Know what your time means.

Durations and clock readings

Enter durations as H:MM or H:MM:SS. Minutes and seconds stay below 60, and hours may exceed 24. Decimal arithmetic avoids binary rounding during intermediate work. Durations display milliseconds, decimal amounts display up to six places, and frame durations display up to six fractional seconds.

Clock-reading tools use fixed arithmetic. A day is 24 hours and a week is 7 days in the unit converter. These values do not describe every real calendar day when daylight saving changes.

Calendar dates

Dates use the ISO Gregorian calendar. Date differences exclude the end date. Business-day calculations let you choose whether to include it. Calendar month arithmetic clamps to the last valid day when the original day is unavailable.

Time zones

City zones follow the rules in your browser’s time-zone database. Fixed abbreviations such as PST (UTC−08:00) do not observe daylight saving. Missing local times are rejected. Repeated times require a choice between earlier and later occurrences.

Timers and sharing

Running duration timers use a finishing timestamp rather than counting each browser tick. Pause stores the remaining duration; resume sets a new finishing timestamp. Deadlines preserve an absolute instant and cannot pause. Your device clock matters.

Timer settings update the address bar. Running timer links retain their absolute finishing time across devices and open as a live countdown. Unstarted duration links begin on opening; paused links keep their remaining time. Shared countdowns stay silent until sound is enabled and do not request screen-awake mode. Copied links capture the current state; later changes do not update previously copied links.

Calculator, stopwatch, and interval links restore editable settings. Session storage restores timing and timer drafts within the same tab, while favourites and display settings stay in local storage.

Estimates

Speech uses the entered words-per-minute rate plus extra pauses. Render estimates assume equal workers and whole frame batches, plus your overhead percentage. Frame conversion uses an explicit frame rate; it does not implement SMPTE or drop-frame timecode.