This looks to be John’s birth here:
https://civilrecords.irishgenealogy.ie/churchrecords/images/birth_retur…
You’ll notice that his date of birth is given as 1st July 1908 (and that the birth was registered on 7th August). The birthdate obviously is a couple of weeks after he appears in the church baptism records. Which appears to be something of a miracle. So what has happened here is that he was probably born on 15th June as the church records show. However there was a small financial penalty if you registered a birth late with the civil authorities. I think it had to be registered within a month or so. So if they were late in registering it, what parents did was simply change the date of birth to one that didn't incur the penalty. So in this particular case they moved his birth date forward by 2 weeks.
The practice was extremely common. If you lived some distance from the Registrar of Births you waited till you were going that way for some other reason and then registered it. That might mean a delay of several months. It’s very common to find births long after a person was baptised.
If you want to order a certified copy of the birth certificate you can do so using this site:
http://www.welfare.ie/en/Pages/Apply-for-Certificates.aspx