ordinal date
Computing term for a date expressed as the day number within the year (e.g., January 1 = 1, December 31 = 365 or 366).
This system stores dates as ordinal dates.
Compound of 年 (year) and 日付 (date), literally 'year date'. The reading ねんひづけ follows standard on'yomi for 年 and the common reading of 日付.