It's Son las veintitrés treinta.
To find the time in the 24-hour clock system, you just have to add 12 hours to the 12-hour clock time. For example, 11:30 p.m, you just add 11:30 + 12, which then equals 23:30. But if it was a.m, in the 24-hour clock system, it'd be the same, like 11:30 a.m would still be 11:30 in the 24-hour clock system. Only p.m times would you add 12 hours to the 12-hour clock time. Hope that helps, lol!