title: Previous date with condition Google Spreadsheet formula
body: <p>I have a list of users with dates of they visited the website.  I need to calculate the first visit date for each record with the condition that if a user misses a month, it is considered new and the date should be new.
  How can I calculate it?</p>
  
  <p>Here is an example. I need to calculate the First visit column. </p>
  
  <pre><code>Visit Date  User    First visit
  10/15/19    User1   10/15/19
  11/13/19    User1   10/15/19
  01/07/20    User1   01/07/20
  02/03/20    User1   01/07/20
  </code></pre>