title: Bash/AWK/SED Match and ReWrite a string of numbers (date) in a line
body: <p>I have a text file with the following contents repeating about 60 times coming from a converted .ics file:</p>
  
  <pre class="lang-none prettyprint-override"><code>Start Vak
  Tijd van: 20120411T093000Z
  Tijd tot: 20120411T100000Z
  Klas(sen) en Docent(en): VPOS0A1 VPOS0A2 Mariel Kers
  Vak: Ex. Verst. beperk.
  Lokaal: 7.05
  Einde Vak
  </code></pre>
  
  <p>I want to rewrite the "Tijd van" and "Tijd tot" values to become a good date (in a bash script on a gnu/linux system with awk,sed and grep etc.). I tried to use awk to find it:</p>
  
  <pre class="lang-sh prettyprint-override"><code>awk '/^Tijd.*[:digit:][:digit:]Z$/; { getline; print $0; }' rooster2.txt
  </code></pre>
  
  <p>and grep:</p>
  
  <pre class="lang-sh prettyprint-override"><code>egrep '/^Tijd(.*)[:digit:][:digit:]Z$/' rooster2.txt
  </code></pre>
  
  <p>But they both do not even find the line. </p>
  
  <p>What I want is to get that date rewritten to a more bash parsable/feasible time format like the EPOCH or something like 31.04.2012 13:00:00. I do not want to replace or rewrite the whole line, just the specific string! Anything, either tips, examples or links are welcome and very usefull. </p>