Transition to global measurement harmony typically falls into one of three common categories:
The first category is the quick Big-Bang scheme which India prefers in the 1960s as well as several other nations including Australia and New Zealand since then.

The second category is to gradually phase in units over time and progressively outlaw traditional units. Industrial nations prefer this scheme, but it is generally less complete and slower.
Japan has been at it for over a hundred years and their status of metrication is “almost entirely complete” — now that is pretty slow!
The third category is to redefine traditional units in metric terms. Places like China where traditional units are ill defined and have regional variations find success with this method.