Mystic 153 calendar

A Himalayan monastery reckoned time by a calendar with a year divided into 153 parts called gongs. Every gong, a monk would strike the temple gong.
The lama was asked about this method of time-keeping. He explained that seeing M months transpire after N gongs would portend that N months would transpire after M years. In effect, the gong-lunar cycle is analogous to the luni-solar cycle. What is the mean year of this calendar?