Ditto Peg M.
Next, the reason why kids have to be potty trained by a certain age is not developmental based... but because kids are going to Preschool. And MOST Preschools, do not accept children in diapers. I know of many Preschools... that even say NO DIAPERS for 2 year olds! Egad... that is just sooooooo unrealistic. Then back home, the parents and child are super stressed... and the parent thinking their kid is slow or dumber than the others who are potty trained, or that their kid is just "stubborn" or they put labels on their kid. But it is not warranted nor age appropriate.
Your child has a "deadline" to be completely trained by August. A child does not know what a deadline is. And if they are stressed about it, they are more likely to NOT want to, or they will get anxiety.
To me as well, being "potty trained" means, that a child can AT-WILL know that they have to pee/poop, AND take themselves to the toilet, be ABLE to pull down their clothes, AND be fully able to "wipe" themselves for both pee and poop.... and then put their clothes back on too. Then wash their hands etc. But even if they do know this and are able to do it... a young child will STILL have accidents. So you have to accept that. Even Kindergarten kids have accidents. Then meanwhile, for night-time.... "dryness" is not even fully developed biologically until even 7 years old. Thus many kids, even Kinder kids, still wear diapers at night. So, its a process.....
All I know is, (I have 2 kids), we can't make them potty competent or able, nor 100% perfection. My son, is 3.5 years old. And only recently, on his own, has he began using the toilet and "wanting" to. But he will not always want to, nor always want to poop on it. And he is NOT dry during the night, yet... nor during naps. Yet.
Encourage.... but do not punish for any disappointments "you" have about it in your mind. Don't show him you are let down about it or stressed.... Or he will be discouraged too.
All the best,
Susan