The Junagarh inscription goes on to tell us that during the reign of R

The Saka era is a historical calendar era. Its epoch (year 0 or year 1) is widely accepted to correspond to 78 CE.
To convert a year in the Saka era to a year in the Common Era (CE), you typically add 78 to the Saka year.

Given Saka era year = 72.
Time in CE = Saka year + 78
Time in CE = 72 + 78
Time in CE = 150 CE.

Therefore, the terrible storm mentioned in the Junagarh inscription occurred in 150 CE.