title: Flutter - showDatePicker set first day of week to Monday
body: <p>I am using the flutter <code>showDatePicker</code> widget <a href="https://api.flutter.dev/flutter/material/showDatePicker.html" rel="noreferrer">https://api.flutter.dev/flutter/material/showDatePicker.html</a> </p>
  
  <p>When the date picker popup loads by default the start of the week is Sunday, I would like to change this to Monday.</p>
  
  <p>Any suggestions on how I can achieve this?</p>
  
  <pre class="lang-dart prettyprint-override"><code>Future&lt;void&gt; _selectDate(BuildContext context) async {
      final DateTime picked = await showDatePicker(
        context: context,
        initialDate: _selectedDate,
        firstDate: firstDate,
        lastDate: lastDate,
        locale: const Locale('en', 'GB'),
      );
      if (picked != null &amp;&amp; picked != _selectedDate) {
        // update the calendar slider with new date
        setState(() {
          _selectedDate = picked.add(Duration(hours: 1));
        });
      }
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/DvHlg.png" rel="noreferrer"><img src="https://i.stack.imgur.com/DvHlg.png" alt="enter image description here"></a> </p>