Date difference calculator — duration between two datetimes (local)
Pick a start and end instant with datetime-local controls (local wall time). See signed milliseconds, exact day/hour/minute/second breakdown, calendar years/months/days, and decimal day/hour/week totals with copy — computed only in your tab.
Frequently asked questions
No. Duration math uses only your browser’s `Date` APIs in this tab. Nothing is sent to LocalTools servers for processing.
Exact breakdown is a fixed millisecond span split into 24-hour days; calendar breakdown borrows across variable month lengths in your local timezone.