#!/bin/bash
text='Time: 00:23PM
Time: 03:23PM
Time: 11:23PM
Time: 12:23PM
Time: 13:45PM'
perl -pe 's/(?<!\d)(0?\d|1[01])(?=:[0-5]?\d\s*PM)/$1+12/ge' <<< "$text"
IyEvYmluL2Jhc2gKdGV4dD0nVGltZTogMDA6MjNQTQpUaW1lOiAwMzoyM1BNClRpbWU6IDExOjIzUE0KClRpbWU6IDEyOjIzUE0KVGltZTogMTM6NDVQTScKcGVybCAtcGUgJ3MvKD88IVxkKSgwP1xkfDFbMDFdKSg/PTpbMC01XT9cZFxzKlBNKS8kMSsxMi9nZScgPDw8ICIkdGV4dCI=