The Chinese system during the imperial period was based on the sitting emperor's reign. The count began on an emperor's official ritual start date, and was based on the sexegenery cycle. The cycle utilized the 10 stems and 12 branches system to pass through 60 day cycles, and then 60 year cycles. So, the first day of the emperor's reign (or reign period, as some emperors had multiple ritualized reign periods) would be listed as the XXX day of the first year of XXX's reign. We also might be told what year it was in the cycle.
With this information from the histories, we can thus pinpoint to the day every dated reference from the Han dynasty onward. The wiki page has some further technical information: http://en.wikipedia.org/wiki/Chinese_calendar
hi! not discouraging any direct responses regarding your specific examples, but you'll find some examples in the FAQ
Removed for trivia seeking.