Starting with custom start date, can I have youth intake? (fast help neede)

So I want to start with club end of this season, but also need youth intake as I will pick lower div team.
What is the latest date I need to date to have youth intake? Or it will not happen if using custome date from here?
Tried 6th march, but youth didint come on 7th, or it is on other date?
Playing in England.

I've found if I choose a date in 2017 it doesn't seem to work.

It won't happen until the following year.