This is a linked open data (LOD) about date and time. "C.E. 0001 January 01" is a date of Julian/Gregorian Calendar (reformed in 1582) (Calendar ID: 101.1).
http://datetime.hutime.org/calendar/101.1/date/C.E._0001_January_01
hcal:101.1/date/1721423.5
hcal:101.1/date/C.E._0001_January_01
hcaldate:1721423.5
hcaldate:C.E._0001_January_01