This is a linked open data (LOD) about date and time. "C.E. 1806 February 17" is a date of Gregorian Calendar (Calendar ID: 2.1).
http://datetime.hutime.org/calendar/2.1/date/C.E._1806_February_17
hcal:2.1/date/2380734.5
hcal:2.1/date/C.E._1806_February_17
hcaldate:2380734.5
hcaldate:C.E._1806_February_17