If you want to convert the time string "12:18 AM" to a date for the current day then you can proceed as follows:
NSString *time = @"12:18 AM";
NSDateFormatter *fmt = [[NSDateFormatter alloc] init];
[fmt setLocale:[NSLocale localeWithLocaleIdentifier:@"en_US_POSIX"]];
// Get year-month-day for today:
[fmt setDateFormat:@"yyyy-MM-dd "];
NSString *todayString = [fmt stringFromDate:[NSDate date]];
// Append the given time:
NSString *todaysTime = [todayString stringByAppendingString:time];
// Convert date+time string back to NSDate:
[fmt setDateFormat:@"yyyy-MM-dd h:mm a"];
NSDate *date = [fmt dateFromString:todaysTime];