Here is what the FA says on ages for players over there:
The relevant age for each Player is determined by his or her age as at midnight on 31 August of the relevant Playing Season i.e. children who are aged 6 as at midnight on 31 August in a Playing Season (together with those who attain the age of 6 during the Playing Season) will be classed as Under 7 Players for that Playing Season. Children who are aged 7 as at midnight on 31 August in a Playing Season will be classed as Under 8 Players for that Playing Season, and so on.
So when they say 05’s it likely means Sept-Dec 05.
The relevant age for each Player is determined by his or her age as at midnight on 31 August of the relevant Playing Season i.e. children who are aged 6 as at midnight on 31 August in a Playing Season (together with those who attain the age of 6 during the Playing Season) will be classed as Under 7 Players for that Playing Season. Children who are aged 7 as at midnight on 31 August in a Playing Season will be classed as Under 8 Players for that Playing Season, and so on.
So when they say 05’s it likely means Sept-Dec 05.