Change a Number inside a Variable
<p>I have the following problem: (Its about dates)
The user will set the following variable.</p>

<blockquote>
  <p>variable1=33_2016</p>
</blockquote>

<p>now I Somehow want to to automatically set a second variable which sets the "33" +1
that I get </p>

<blockquote>
  <p>variable2=34_2016</p>
</blockquote>

<p>Thanks for any advice.</p>