Dropdown-div-based/index.html

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8" />
		<meta http-equiv="X-UA-Compatible" content="IE=edge" />
		<title>Div Dropdown</title>
		<meta name="viewport" content="width=device-width, initial-scale=1" />
		<link rel="stylesheet" type="text/css" media="screen" href="app.css" />
	</head>
	<body>
		<div class="events">
			<div class="years select">
				<div id="year-2020" class="year active">2020</div>
				<div id="year-2019" class="year">2019</div>
				<div id="year-2018" class="year">2018</div>
				<div id="year-2017" class="year">2017</div>
			</div>

			<div class="months select">
				<div id="jan" class="event show active">January</div>
				<div id="feb" class="event">February</div>
				<div id="mar" class="event">March</div>
				<div id="apr" class="event">April</div>
				<div id="may" class="event">May</div>
				<div id="jun" class="event">June</div>
				<div id="july" class="event">July</div>
				<div id="aug" class="event">August</div>
				<div id="sep" class="event">September</div>
				<div id="oct" class="event">October</div>
				<div id="nov" class="event">November</div>
				<div id="dec" class="event">December</div>
			</div>
		</div>
		<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
		<script src="app.js"></script>
	</body>
</html>