Unchecking of the checked checkboxes on another button click

I want the checked checkboxes to be unchecked on clicking another button:

Below is the HTML

<input type="checkbox" name="checkb" id="Agent" value="Agent"> type=Agent
<br />

  <input type="checkbox" name="checkb" id="Customer" value="Customer"> type=Customer
<br />

  <input type="checkbox" name="checkb" id="Phone" value="Phone"> type=Phone
<br />

  <input type="checkbox" name="checkb" id="ID_Card" value="ID_Card"> type=ID_Card
<br />

<input type=datetime id="Start_Date" value="" placeholder="Start_Date" />
<input type=datetime id="End_Date" value="" placeholder="End_Date" />
<button id="date">
  Interval
</button>

On clicking of the Interval button if any checkboxes are checked they should get unchecked.

Below is the event listener for the Interval button:

           var check1 = document.getElementById("Agent");
var check2 = document.getElementById("Customer");
var check3 = document.getElementById("Phone");
var check4 = document.getElementById("ID_Card");


var newBtn = document.getElementById("date");
if (newBtn) {
  newBtn.addEventListener("click", function() {

    if (check1.checked) {
      var ischecked1 = check1.checked;

      check1.checked != ischecked1;
    }
    if (check2.checked) {
      var ischecked2 = check2.checked;

      check2.checked != ischecked2;

    }

    if (check3.checked) {
      var ischecked3 = check3.checked;

      check3.checked != ischecked3;
    }
    if (check4.checked) {
      var ischecked4 = check4.checked;

      check4.checked != ischecked4;

    }
  });
}

Below code runs without any errors, but the boxes do not get unchecked if they are checked.

Below is the fiddle