title: Flutter How can I change the start and end day of the week?
body: <p>I am developing a company app, but this company starts on Saturday and finishes on Thursday.Friday is a holiday.  6 day works.</p>
  <p>I am using Jiffy package cause I need control the week number.
  Start of week day monday and finish of week day Thursday.
  I working API
  and API connect Mysql. Mysql working same we changed the start of week day and finish day of the week.</p>
  <p>But problem is  i need the send same week number. Every after the Friday
  the week number is always missing.</p>
  <p>How can I change in flutter the start of week day and the finish of week day ?</p>