WHV (UK) – When does the 12 month period start?

Hi all – I’m considering doing a ski season in Japan next winter (25/26). I am trying to work out when the 12 month visa period begins from; is this the point at which I pick up my passport from the embassy, or from when I enter Japan?

With the Canadian WHV for example you are provided a port of entry letter which you then have 12 months to ‘activate’ into the 2 year visa by arriving into Canada.

Is this the same with Japan ie. Once passport collected from the embassy you have a period of time upon which to enter the country, and then once you do you are allowed to stay for 12 months?

Reason for asking is that I am 30, about to turn 31, and so have to apply for the visa before my birthday.

Thanks!