This is a linked open data (LOD) about date and time. "C.E. 2013 May" is a month of Gregorian Calendar (Calendar ID: 2.1).
http://datetime.hutime.org/calendar/2.1/month/C.E._2013_May
hcal:2.1/month/2456413.5
hcal:2.1/month/C.E._2013_May
hcalmonth:2456413.5
hcalmonth:C.E._2013_May