Are there any mom's on this group whose babies were due in July but babies ended up being born in June?

My baby was due July 10th but born 30th June. Am a bit still confused about which group to use as orientation. It seems he is too young for the June group but too old for this one. June babies are having milestones he hasn't quite had yet and yet July babies aren't at his level either. How do you guys do it if your kids were born end June beginning July? Which group is more relevant to our child's developmental stage or are you in both?