Time in Tibetan Medicine

The explanation of how diseases occur, behavior,  diet and so on depend largely upon seasonal change. Time therefore plays are very important role in Tibetan Medicine. 

However, the basis of time is covered only very briefly in the seasonal conduct chapter of the explanatory tantra:

A kṣana, and so on, become a lava, a muhūrta, ahorata, a month, a season, and a year...

Here, I have chosen to give the Sanskrit terms rather than attempting to represent first four items in English because there are no precise English equivalents.

So, what is the basis of measuring of the most basic unit of time in Buddhism, the kṣana? The basis of measuring the kṣana is the duration of a single mental concept. A kṣana equals 0.0013 seconds. How do we know this? 120 kṣanas equals on tatkṣana; 60 tatkṣanas equal a lava; 30 lava equal a muhurta; 30 muhurtas equal an ahorata, which is a single 24 hour period of time. So, according to Buddhist principles then, a moment of thought has a duration of 0.0013 seconds.

What is more interesting, however, is that this length of a mental concept, a kṣana, is held to be the basic unit by which all other units of time are measured.