There is a leap year every four years in which the 13th month will gain a 6th day. The current year is 1991 which is a leap year. ANSI C computer code for Ethiopian and Gregorian calendar conversions, with Ethiopic formatting utilities, may be found here here. Abbreviated day of week and month names are rarely practiced. Under extreme space limitations the days of the week and month names will be simply truncated to fit the available space while the truncated name remains uniquely identifiable.
Tigrigna truncations require two letters for the day of week name.
Ethiopic numerals are not used in digital clocks for hours, minutes, seconds. English numerals are used. Ethiopic numerals are used for dates of the month and years. Users would likely want the option to toggle between both. Each day of the month has a proper name under Orthodox Christian practices.