Question
When do the Copts celebrate Christmas?
Answer
25 days of December Julian Calendar.1
If you live in nations using Gregorian Calendar, such as, Indonesia and USA, convert the date with Calender Converter tool.

Bibliografi
1http://www.copticchurch.net/topics/coptic_calendar/nativitydate.html ; access 5/15/2015
2http://www.calendarhome.com/calculate/convert-a-date/ ; access 5/15/2015