Second date is the cover date. It appears there was a production error and "September" was used instead of "July".
in 52 (DC, 2007 series) #1 ([May] 2007)
in The 52 Omnibus (DC, 2012 series) #[nn] (October 2012)
in 52 (DC, 2007 series) #1 ([May] 2007)
in The 52 Omnibus (DC, 2012 series) #[nn] (October 2012)
in 52 (ECC Ediciones, 2012 series) #1 (Octubre 2012)