Julian Date Converter – Convert Gregorian Date to Julian Date

Julian Date Converter Julian Date Converter

Thirteen-month calendar

Coptic Date Converter

Convert Gregorian dates into Coptic calendar dates, or convert Coptic dates back into Gregorian dates.

Enter a Gregorian date to return the matching Coptic calendar date.

Live output

Result

Ready to convert

Choose a direction, enter a Gregorian or Coptic date, and the result appears here without leaving the page.

Guide

Convert Coptic calendar dates and Gregorian dates

This Coptic Date Converter changes Gregorian dates into Coptic calendar dates and converts Coptic input back into Gregorian dates. It is useful for checking Coptic calendar references, comparing civil dates, and validating dates that include the short thirteenth month.

The Coptic calendar has twelve 30-day months plus a short epagomenal month, Pi Kogi Enavot. The converter supports month 13 and validates reverse input through ICU so that impossible Coptic dates do not silently shift.

This page uses ICU's coptic calendar implementation. It focuses on date conversion, not on calculating liturgical observances, fasting periods, or church calendar events.

What it handles

Coptic calendar conversion coverage

The converter supports Gregorian to Coptic and Coptic to Gregorian conversion with the same ICU-backed calendar basis in both directions. Results include the Coptic year, month, day, month name, weekday, and era label.

Because the thirteenth month is shorter than normal months, reverse conversion must validate more than just the numeric range. The converter checks that ICU returns the same Coptic date that was entered.

Gregorian to Coptic

Enter a Gregorian date and return the matching Coptic calendar date with month label and weekday.

Coptic to Gregorian

Enter a Coptic date in YYYY-MM-DD format and convert it back into Gregorian form.

Epagomenal month support

The short thirteenth month is supported and validated against the Coptic year entered.

How to use

Use the Coptic conversion modes

Choose Gregorian to Coptic when your source date is Gregorian. Choose Coptic to Gregorian when you already have a Coptic year, month, and day value.

Coptic input uses YYYY-MM-DD with month numbers 01 through 13. Use leading zeroes for month and day, and remember that month 13 has only a small number of valid days.

1

Choose Gregorian to Coptic

Use this direction for a Gregorian date such as 2026-06-30. The result is Coptic 1742-10-23.

2

Choose Coptic to Gregorian

Use this direction for Coptic input such as 1742-10-23. The converter returns the matching Gregorian date.

3

Validate thirteenth-month dates

If a Pi Kogi Enavot date is outside the valid day range for the year, the converter asks you to correct it.

Examples

Reference conversions from the local implementation

These examples are generated from the same ICU-backed conversion functions used by the form. They show the Coptic date returned for a modern Gregorian date and the matching reverse lookup.

Gregorian date to Coptic date

2026-06-30 -> 1742-10-23

The Gregorian date 2026-06-30 converts to Coptic 1742-10-23.

Coptic date to Gregorian date

1742-10-23 -> 2026-06-30

The Coptic input 1742-10-23 converts back to Gregorian 2026-06-30.

FAQ

Coptic date conversion notes

Coptic date conversion can be confused with Ethiopian conversion because both calendars have thirteen months and related structures. These answers define what this Coptic page handles.

Is the Coptic calendar the same as the Ethiopian calendar?

No. They are related thirteen-month calendars, but this page uses ICU's coptic calendar and Coptic month labels.

Does this support the thirteenth month?

Yes. Month 13 is supported, and invalid thirteenth-month dates are rejected through round-trip validation.

Does this calculate Coptic feast dates?

No. This page converts calendar dates and does not calculate liturgical events or feast-day rules.

Reference

Calendar implementation reference

This converter uses ICU calendar services through PHP Intl. ICU documents the coptic calendar identifier and field behavior used by the converter for validation and date conversion.