Coptic Date Difference Calculator

Enter the date values and the tool computes the result for the coptic calendar system.

1. 1

   Step 1

   Enter both dates in full under the Coptic calendar: day, month, and year each.

2. 2

   Step 2

   We walk the real Coptic calendar — 12 × 30-day months plus 5–6 short epagomenal days — instead of a flat 30-day-month average.

3. 3

   Step 3

   Read the result exact to the day — Coptic leap years (365–366 days) applied automatically.

• 1

  This Coptic Date Difference follows Coptic calendar rules — its own epoch, month lengths, and leap years — so the result can differ from a Gregorian-based calculation of the same date; treat the calendar system as part of the input.

• 2

  Watch century boundaries and very old dates in the Coptic system: historical calendars dropped or added days when they were adopted, which is invisible in daily use but material for long-range historical calculations here.

• 3

  Enter the Coptic dates in YYYY-MM-DD format to avoid ambiguity — some conventions read 03/04 as March fourth and others as April third, and a swapped month and day silently shifts every result this page derives.

• Inclusive versus exclusive counting: two endpoints five days apart yield 4 or 5 days depending on whether the last day counts. Decide the convention for your Coptic calculation first — contracts and payroll rarely agree on it.

• Reusing a memorized constant — fixed day counts, epoch offsets — instead of the Coptic rules drifts silently across years because leap days accumulate differently per system. Recompute with the tool rather than adding offsets by hand.