Ask HN: When is the right time to think about localisation

I'm currently working on a prototype for a consumer facing application which hopefully will have global applicativity.

I've often heard the adage that it is never too soon to worry about localisation and timezones, but am wondering whether when trying to develop a MVP whether this holds.

I know there are a number of founders here, so would like ask: "When did you start worrying about localisation? Would you have approached localisation differently if you were to start over again?"