Ordinal dates

The ordinal date <https://en.wikipedia.org/wiki/Ordinal_date> specifies the day of year as a number between 1 and 366.

Ordinal dates are represented by a tuple: (year, dayofyear)

convertdate.ordinal.from_gregorian(year, month, day)

Convert a Gregorian date to an ordinal date.

convertdate.ordinal.from_jd(jd)

Convert a Julian day count to an ordinal date.

convertdate.ordinal.to_gregorian(year, dayofyear)

Convert an ordinal date to a Gregorian date.

convertdate.ordinal.to_jd(year, dayofyear)

Return Julian day count of given ordinal date.