First day of previous month as paramter

Migrateduser

<p>Hi</p>
<p> </p>
<p>I'm trying to have the first day of the previous month by default parameter.</p>
<p>If I run my report today, my parameter will be 2016-12-01.</p>
<p>Idea?</p>
<p> </p>
<p>Martin</p>