the interval between two identical moon phases as observed from Earth: 29 days, 12 hours, 44 minutes, 2.9 seconds (29.53059 days)
this is the fundamental time unit of the lunar machine time system — the DD position counts days within one synodic month
the synodic period differs from the sidereal month (27.32 days) because Earth moves along its orbit while the moon completes its cycle, requiring additional angular travel to reach the same Sun-Moon-Earth geometry
see moon, calendar, lunar-based