<form>
	<div>
		<label for="date">Date <span class="description-date">Please use the YYYY-MM-DD format.</span></label>
		<input type="date" id="date" pattern="(?:19|20)[0-9]{2}-(?:(?:0[1-9]|1[0-2])-(?:0[1-9]|1[0-9]|2[0-9])|(?:(?!02)(?:0[1-9]|1[0-2])-(?:30))|(?:(?:0[13578]|1[02])-31))" required>
	</div>

	<input type="submit" class="button" value="Submit">
</form>
body {
	font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen", "Ubuntu", "Cantarell", "Fira Sans", "Droid Sans", "Helvetica Neue", sans-serif;
	font-size: 112.5%;
	margin-left: auto;
	margin-right: auto;
	max-width: 40em;
	width: 88%;
}  

/**
 * Form Styles
 */
label {
	display: block;
	font-weight: bold;
	margin-bottom: 0.5em;
}

.label-normal {
	font-weight: normal;
}

.description-date {
	color: #808080;
	font-size: 0.8em;
	font-weight: normal;
}

.supports-color .color,
.supports-date .date,
.supports-time .time,
.supports-month .mont {
	display: none;
}

input,
select {
	display: inline-block;
	font-size: 1em;
	margin-bottom: 1em;
	padding: 0.25em 0.5em;
	width: 100%;
}

[type="checkbox"],
[type="radio"] {
	margin-bottom: 0.5em;
	width: auto;
}

.button {
	background-color: #0088cc;
	border: 1px solid #0088cc;
	border-radius: 1px;
	color: #ffffff;
	display: inline-block;
	font-size: 0.9375em;
	font-weight: normal;
	line-height: 1.2;
	margin-right: 0.3125em;
	margin-bottom: 0.3125em;
	padding: 0.5em 0.6875em;
	width: auto;
}

.button:active,
.button:focus,
.button:hover {
	background-color: #005580;
	border-color: #005580;
	color: #ffffff;
	text-decoration: none;
}

.button:active {
	box-shadow: inset 0 0.15625em 0.25em rgba(0, 0, 0, 0.15), 0 1px 0.15625em rgba(0, 0, 0, 0.05);
}

External CSS

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External JavaScript

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