title: Convert all XML dates in file to normal dates (dd-mm-yyyy)
body: <p>Hello dear Stack community</p>
  <p>I used an app to create a calendar backup a long time ago but I'm now unable to recover the backup in that same app for some reason. So I now want to replace all the dates from the ''calendar.xml'' file to a more normal date format such as dd-mm-yyyy so I can search the text file quickly for a given day of the year. If anyone has an idea of a code that I run to accomplish that, it would be grandly appreciated. I attached the beginning of the xml file with the first 2 entries for reference.</p>
  <p>Thank you in advance</p>
  <pre><code>&lt;?xml version='1.0' encoding='UTF-8' standalone='yes' ?&gt;
  &lt;root&gt;
    &lt;calendar_entry&gt;
      &lt;title&gt;No school&lt;/title&gt;
      &lt;start_date&gt;1364774400&lt;/start_date&gt;
      &lt;end_date&gt;1364774405&lt;/end_date&gt;
      &lt;description&gt;&lt;/description&gt;
      &lt;time_zone&gt;UTC&lt;/time_zone&gt;
      &lt;location&gt;&lt;/location&gt;
      &lt;rrule /&gt;
      &lt;all_day&gt;true&lt;/all_day&gt;
    &lt;/calendar_entry&gt;
    &lt;calendar_entry&gt;
      &lt;title&gt;No school&lt;/title&gt;
      &lt;start_date&gt;1366934400&lt;/start_date&gt;
      &lt;end_date&gt;1366934401&lt;/end_date&gt;
      &lt;description&gt;&lt;/description&gt;
      &lt;time_zone&gt;UTC&lt;/time_zone&gt;
      &lt;location&gt;&lt;/location&gt;
      &lt;rrule /&gt;
      &lt;all_day&gt;true&lt;/all_day&gt;
    &lt;/calendar_entry&gt;
    ...
  &lt;/root&gt;
  </code></pre>