Hi !!
7:30 p.m. = Il est sept heures et demie du soir.
sept heures trente is correct as well, but I think , at school, you've to learn "et quart" , "moins le quart", "et demie" ......
As in French school , we have to learn the proper way to say the hours as "it's half past seven p.m." and not "seven thirty" even though , it's used....
hope I helped !!