Hello Reader's! if you want to make the Date time format validation in your form then you can use Javascript to validate.

Let's see the example below:-

your html will be go like this:-

<form method="POST" action="/javascript/validate-date/" onsubmit="checkForm2(this); return false;">
<fieldset>
<legend>Event Details</legend>
<label for="field_startdate2">Start Date</label><span><input id="field_startdate2" type="text" size="12" placeholder="dd/mm/yyyy" name="startdate"> <small>(dd/mm/yyyy)</small></span>
<label for="field_starttime2">Start Time</label><span><input id="field_starttime2" type="text" size="12" name="starttime"> <small>(eg. 01:36 or 1:36am)</small></span>
<span><input type="submit"></span>
</fieldset>
</form>   

And your javascript will go like this:-

<script type="text/javascript">

      function checkForm(form)
      {
        // regular expression to match required date format
        re = /^(\d{1,2})\/(\d{1,2})\/(\d{4})$/;

        if(form.startdate.value != '') {
          if(regs = form.startdate.value.match(re)) {
            // day value between 1 and 31
            if(regs[1] < 1 || regs[1] > 31) {
              alert("Invalid value for day: " + regs[1]);
              form.startdate.focus();
              return false;
            }
            // month value between 1 and 12
            if(regs[2] < 1 || regs[2] > 12) {
              alert("Invalid value for month: " + regs[2]);
              form.startdate.focus();
              return false;
            }
            // year value between 1902 and 2015
            if(regs[3] < 1902 || regs[3] > (new Date()).getFullYear()) {
              alert("Invalid value for year: " + regs[3] + " - must be between 1902 and " + (new Date()).getFullYear());
              form.startdate.focus();
              return false;
            }
          } else {
            alert("Invalid date format: " + form.startdate.value);
            form.startdate.focus();
            return false;
          }
        }

        // regular expression to match required time format
        re = /^(\d{1,2}):(\d{2})([ap]m)?$/;

        if(form.starttime.value != '') {
          if(regs = form.starttime.value.match(re)) {
            if(regs[3]) {
              // 12-hour value between 1 and 12
              if(regs[1] < 1 || regs[1] > 12) {
                alert("Invalid value for hours: " + regs[1]);
                form.starttime.focus();
                return false;
              }
            } else {
              // 24-hour value between 0 and 23
              if(regs[1] > 23) {
                alert("Invalid value for hours: " + regs[1]);
                form.starttime.focus();
                return false;
              }
            }
            // minute value between 0 and 59
            if(regs[2] > 59) {
              alert("Invalid value for minutes: " + regs[2]);
              form.starttime.focus();
              return false;
            }
          } else {
            alert("Invalid time format: " + form.starttime.value);
            form.starttime.focus();
            return false;
          }
        }

        alert("All input fields have been validated!");
        return true;
      }

    </script>

Now if the user will make incorrect input an alert box will notify it to user.