<form action="https://cs12.net/form/submit.php" method="post">
   <fieldset>
     <legend>Date and Time     </legend>
     <label>Pick a date:
       <input type="date" name="my_date"/>
     </label>
     <label>Pick a datetime
       <input type="datetime-local" name="my_datetime"/>
     </label>
     <label>Pick a time (15 minute increments)
       <input type="time" name="my_time_15" step="900" value="12:00"/>
     </label>
     <label>Pick a time (1 minute increments)
       <input type="time" name="my_time_1" step="60" value="12:00"/>
     </label>
     <label>Pick a time (1 second increments)
       <input type="time" name="my_time_1s" step="1" value="12:00"/>
     </label>   </fieldset>
   <button type="submit">Submit   </button>
 </form>

In style element (<style>) within head element:

label, button { display: block; margin-top: 1rem;}
        input { display: block;  margin-top: 0.25rem;}