In Ethiopia the year have 13 months and but in Gregorian calendar the year have 12 months,
The Ethiopian society's are want to use his Ethiopian calendar year,i have the algorithm,
but the way i add to the postgresql source code as EXTENSION? or to the backend(to kernel)?
13th month have 5 days and in fourth year 13th month have 6 days.that means 1 year have 365.25 days,my algorithm converts Gregorian calendar year to Ethiopian calendar year.
It can be done via extension - you should to implement own date and timestamp type with own input, output functions
