Each upgrade of the youth facility will decrease the wait time by 4 days.

If youth appear on day 1 of new season will lose a star and age 1 year before you get them, so aim for day 2.

level #.........................days until youth appear.......build on day
L0 (Target Shot).......................28.................... ..........27
L3 (Junior Pitch).......................24................... ............3
L5 (Mini Camp).........................20.................. .............7
L7 (Football School)..................16....................... .......11
L10 (Youth Academy)................12........................ ......15