How to count days between two dates

1. Pick the calendar

   "Calendar" supports Gregorian (Miladi), Jalali (Persian / Shamsi), and Hijri (Umm al-Qura). Both the start and end dates are interpreted against the SAME calendar — they're then converted internally to Gregorian instants for the math.

2. Enter start date

   Three integer fields: "Start year" (1–2500), "Start month" (1–12), "Start day" (1–31). The picker UI shows the chosen calendar's month names so you can read the date in familiar form.

3. Enter end date

   Same three fields with `end` prefix. End may equal start (zero-day result) or be before start (negative deltas). Leap days and irregular months in each calendar are handled by the conversion layer.

4. Press Run

   Result returns years/months/days difference plus totalDays, totalWeeks, and totalHours. Use it for tenure, sprint length, savings duration, or visa stays — anything driven by a date span.