In classical Chinese cosmology
日月 are the two great heavenly bodies and stand for time itself. The character
明 ('bright') is famously composed of
日 +
月 - sun next to moon - and the Ming dynasty (
明朝, 1368-1644) is named accordingly. Common four-character chunks:
日月如梭 ('days and months are like a weaver's shuttle' - time flies);
日月同辉 ('shining as bright as sun and moon' - eternal glory).
