diff --git a/includes/sanitizers/class-amp-style-sanitizer.php b/includes/sanitizers/class-amp-style-sanitizer.php
index 56c1560b149..91198e09edf 100644
--- a/includes/sanitizers/class-amp-style-sanitizer.php
+++ b/includes/sanitizers/class-amp-style-sanitizer.php
@@ -661,6 +661,12 @@ private function has_used_class_name( $class_names ) {
 						}
 						continue 2;
 				}
+			} elseif ( ctype_upper( $class_name[0] ) && $this->has_used_tag_names( [ 'amp-date-picker' ] ) && $this->is_class_allowed_in_amp_date_picker( $class_name ) ) {
+				// If the document has an amp-date-picker tag, check if this class is an allowed child of it.
+				// That component's child classes won't be present yet in the document, so prevent tree-shaking valid classes.
+				// The ctype_upper() check is an optimization since we know up front that all class names in React Dates are
+				// in CamelCase form, thus we can short-circut if the first character of the class name is not upper-case.
+				continue;
 			}
 
 			if ( ! isset( $this->used_class_names[ $class_name ] ) ) {
@@ -756,6 +762,32 @@ private function has_used_attributes( $attribute_names ) {
 		return true;
 	}
 
+	/**
+	 * Whether a given class is allowed to be styled in <amp-date-picker>.
+	 *
+	 * That component has child classes that won't be present in the document yet.
+	 * So get whether a class is an allowed child.
+	 *
+	 * @since 1.5.0
+	 * @link https://github.com/airbnb/react-dates/tree/05356/src/components
+	 *
+	 * @param string $class The name of the class to evaluate.
+	 * @return bool Whether the class is allowed as a child of <amp-date-picker>.
+	 */
+	private function is_class_allowed_in_amp_date_picker( $class ) {
+		static $class_prefixes = [
+			'CalendarDay',
+			'CalendarMonth',
+			'CalendarMonthGrid',
+			'DayPicker',
+			'DayPickerKeyboardShortcuts',
+			'DayPickerNavigation',
+			'KeyboardShortcutRow',
+		];
+
+		return in_array( strtok( $class, '_' ), $class_prefixes, true );
+	}
+
 	/**
 	 * Run logic before any sanitizers are run.
 	 *
diff --git a/tests/php/test-amp-style-sanitizer.php b/tests/php/test-amp-style-sanitizer.php
index 319f1a51f08..75259f86142 100644
--- a/tests/php/test-amp-style-sanitizer.php
+++ b/tests/php/test-amp-style-sanitizer.php
@@ -657,6 +657,46 @@ static function( $preempt, $request, $url ) {
 	 */
 	public function get_amp_selector_data() {
 		return [
+			'amp-date-picker-allowed-child-class-not-tree-shaken' => [
+				'<div><amp-date-picker id="baz" type="single" mode="overlay" layout="container" format="YYYY-MM-DD" src="/example.json" input-selector="#src-input"></amp-date-picker></div>',
+				'amp-date-picker .CalendarMonth_caption{border-bottom: 10px} div amp-date-picker .amp-date-picker-selecting{margin-right:10px}',
+				'amp-date-picker .CalendarMonth_caption{border-bottom:10px}div amp-date-picker .amp-date-picker-selecting{margin-right:10px}', // This class is an allowed child, so it shouldn't be removed.
+			],
+			'amp-date-picker-single-allowed-child-class-not-tree-shaken' => [
+				'<div><amp-date-picker id="baz" type="single" mode="overlay" layout="container" format="YYYY-MM-DD" src="/example.json" input-selector="#src-input"></amp-date-picker></div>',
+				'.DayPicker_weekHeaders {border-bottom: 10px}',
+				'.DayPicker_weekHeaders{border-bottom:10px}',
+			],
+			'amp-date-picker-allowed-container-child-class-not-tree-shaken' => [
+				'<div><amp-date-picker id="baz" type="single" mode="overlay" layout="container" format="YYYY-MM-DD" src="/example.json" input-selector="#src-input"></amp-date-picker></div>',
+				'amp-date-picker .amp-date-picker-calendar-container{border-bottom: 10px} div amp-date-picker .amp-date-picker-selecting{margin-right:10px}',
+				'amp-date-picker .amp-date-picker-calendar-container{border-bottom:10px}div amp-date-picker .amp-date-picker-selecting{margin-right:10px}',
+			],
+			'valid-class-wrapping-amp-date-picker-not-tree-shaken' => [
+				'<div class="foo-baz"><amp-date-picker id="baz" type="single" mode="overlay" layout="container" format="YYYY-MM-DD" src="/example.json" input-selector="#src-input"></amp-date-picker></div>',
+				'.foo-baz amp-date-picker .CalendarMonth_caption{border-bottom: 10px} div amp-date-picker .amp-date-picker-selecting{margin-right:10px}',
+				'.foo-baz amp-date-picker .CalendarMonth_caption{border-bottom:10px}div amp-date-picker .amp-date-picker-selecting{margin-right:10px}',
+			],
+			'amp-date-picker-valid-child-tree-shaken-if-component-not-in-document' => [
+				'<div><span>AMP Date Picker Not Present</span></div>',
+				'amp-date-picker .CalendarMonth_caption{border-bottom: 10px}',
+				'',
+			],
+			'amp-date-picker-similar-disallowed-child-class-tree-shaken' => [
+				'<div><amp-date-picker id="baz" type="single" mode="overlay" layout="container" format="YYYY-MM-DD" src="/example.json" input-selector="#src-input"></amp-date-picker></div>',
+				'amp-date-picker .CalendarFoo {border-bottom: 10px}',
+				'',
+			],
+			'amp-date-picker-disallowed-child-class-tree-shaken' => [
+				'<div><amp-date-picker id="baz" type="single" mode="overlay" layout="container" format="YYYY-MM-DD" src="/example.json" input-selector="#src-input"></amp-date-picker></div>',
+				'amp-date-picker .random-class{border-bottom: 10px}',
+				'',
+			],
+			'amp-date-picker-non-children-tree-shaken' => [
+				'<div><amp-date-picker id="example" type="single" mode="static" layout="fixed-height" height="150" format="YYYY-MM-DD"></amp-date-picker></div>',
+				'amp-date-picker .CalendarMonth_caption{border-bottom: 10px} .unrelated{color:#fff}',
+				'amp-date-picker .CalendarMonth_caption{border-bottom:10px}', // Non-children of the amp-date-picker should still be tree-shaken if they're not in the DOM.
+			],
 			'img' => [
 				sprintf( '<div><img class="logo" src="%s" width="200" height="100"></div>', admin_url( 'images/wordpress-logo.png' ) ),
 				'div img.logo{border:solid 1px red}',