Here's my solution in Java:

public static String timeConversion(String s) {
    String meridiem = s.substring(8);
    int hours = Integer.parseInt(s.substring(0, 2));
    String colonsMinutesAndSeconds = s.substring(2, 8);

    if (meridiem.equals("AM") && hours == 12) {
        hours = 0;
    } else if (meridiem.equals("PM") && hours != 12) {
        hours += 12;
    }

    return String.format("%02d%s", hours, colonsMinutesAndSeconds);
}

My short answer…

def timeConversion(s):
    return f'{int(s[:2]) % 12 + (0 if s[-2:] == "AM" else 12):02}' + s[2:8]

def timeConversion(s): # Write your code here meridian = s[8:10] print(s[2:7]) hour_given = int(s[0:2]) hour_computed = hour_given%12 if meridian=='AM' else ((hour_given%12)+12) return str(hour_computed).zfill(2)+s[2:8]

Using datetime tools:

import os
import datetime

def timeConversion(s):
    time_format = "%H:%M:%S"
    dt_s = datetime.datetime.strptime(s, "%I:%M:%S%p")
    return datetime.datetime.strftime(dt_s, time_format)

if __name__ == '__main__':
    fptr = open(os.environ['OUTPUT_PATH'], 'w')

    s = input()
    result = timeConversion(s)

    fptr.write(result + '\n')
    fptr.close()

JavaScript

function timeConversion(s) {

let [hours, minutes, seconds] = s.split(':');

if (hours === '12'){
    hours = '00';
}

if (seconds.indexOf('PM')  != -1 && hours < 12 ){
    hours = parseInt(hours, 10) + 12;
}

let conversion = ``${hours}:$`{minutes}:${seconds}`

return conversion.slice(0, -2);

}