To investigate the question whether the date used in Chinese historical annals when recording an observation made during the latter half of the night is the old date or the new date, 139 records of occultations of planets or stars by the Moon when the latter is more than 18 days old were picked out from a total of 645 occultation records found in the dynastic histories. For these 139 events, the date of occurence, the local time and the altitude of the Sun etc. were re-calculated from modern lunar and planetary tables. The overall results is that 85% of the records use the old date and only 15% use the new date; but during the two periods 300–550 (the Southern and Northern Dynasties) and 1000–1250 (The greater part of the Song Dynasty), the proportion of new dates was even less. For the other periods, the great majority of the events dated with the new date took place after 3 a.m. Local Time, or when the Sun's altitude was greater than −35°. Details in Fig. 2.