Date: Add timezone hint

lib/compat.php

@@ -333,6 +333,77 @@ function gutenberg_add_dom_rect_polyfill( $scripts ) {
 }
 add_action( 'wp_default_scripts', 'gutenberg_add_dom_rect_polyfill', 20 );
 
+/**
+ * Adds a wp.date.setSettings with timezone abbr parameter
+ *
+ * This can be removed when plugin support requires WordPress 5.6.0+.
+ *
+ * The script registration occurs in core wp-includes/script-loader.php
+ * wp_default_packages_inline_scripts()
+ *
+ * @since 8.6.0
+ *
+ * @param WP_Scripts $scripts WP_Scripts object.
+ */
+function gutenberg_add_date_settings_timezone( $scripts ) {
+	if ( ! did_action( 'init' ) ) {
+		return;
+	}
+
+	global $wp_locale;
+
+	// Calculate the timezone abbr (EDT, PST) if possible.
+	$timezone_string = get_option( 'timezone_string', 'UTC' );
+	$timezone_abbr   = '';
+
+	if ( ! empty( $timezone_string ) ) {
+		$timezone_date = new DateTime( null, new DateTimeZone( $timezone_string ) );
+		$timezone_abbr = $timezone_date->format( 'T' );
+	}
+
+	$scripts->add_inline_script(
+		'wp-date',
+		sprintf(
+			'wp.date.setSettings( %s );',
+			wp_json_encode(
+				array(
+					'l10n'     => array(
+						'locale'        => get_user_locale(),
+						'months'        => array_values( $wp_locale->month ),
+						'monthsShort'   => array_values( $wp_locale->month_abbrev ),
+						'weekdays'      => array_values( $wp_locale->weekday ),
+						'weekdaysShort' => array_values( $wp_locale->weekday_abbrev ),
+						'meridiem'      => (object) $wp_locale->meridiem,
+						'relative'      => array(
+							/* translators: %s: Duration. */
+							'future' => __( '%s from now', 'default' ),
+							/* translators: %s: Duration. */
+							'past'   => __( '%s ago', 'default' ),
+						),
+					),
+					'formats'  => array(
+						/* translators: Time format, see https://www.php.net/date */
+						'time'                => get_option( 'time_format', __( 'g:i a', 'default' ) ),
+						/* translators: Date format, see https://www.php.net/date */
+						'date'                => get_option( 'date_format', __( 'F j, Y', 'default' ) ),
+						/* translators: Date/Time format, see https://www.php.net/date */
+						'datetime'            => __( 'F j, Y g:i a', 'default' ),
+						/* translators: Abbreviated date/time format, see https://www.php.net/date */
+						'datetimeAbbreviated' => __( 'M j, Y g:i a', 'default' ),
+					),
+					'timezone' => array(
+						'offset' => get_option( 'gmt_offset', 0 ),
+						'string' => $timezone_string,
+						'abbr'   => $timezone_abbr,
+					),
+				)
+			)
+		),
+		'after'
+	);
+}
+add_action( 'wp_default_scripts', 'gutenberg_add_date_settings_timezone', 20 );
+
 /**
  * Filters default block categories to substitute legacy category names with new
  * block categories.

packages/components/package.json

@@ -32,6 +32,7 @@
 		"@emotion/styled": "^10.0.23",
 		"@wordpress/a11y": "file:../a11y",
 		"@wordpress/compose": "file:../compose",
+		"@wordpress/date": "file:../date",
 		"@wordpress/deprecated": "file:../deprecated",
 		"@wordpress/dom": "file:../dom",
 		"@wordpress/element": "file:../element",

packages/components/src/date-time/style.scss

@@ -186,6 +186,13 @@
 	}
 }
 
+.components-datetime__timezone {
+	color: $dark-gray-500;
+	line-height: 30px;
+	margin-left: $grid-unit-05;
+	text-decoration: underline dotted;
+}
+
 .components-datetime__time-legend {
 	font-weight: 600;
 	margin-top: 0.5em;

packages/components/src/date-time/test/__snapshots__/time.js.snap

@@ -156,6 +156,7 @@ exports[`TimePicker matches the snapshot when the is12hour prop is false 1`] = `
           value="00"
         />
       </div>
+      <TimeZone />
     </div>
   </fieldset>
 </div>
@@ -337,6 +338,7 @@ exports[`TimePicker matches the snapshot when the is12hour prop is specified 1`]
           PM
         </ForwardRef(Button)>
       </ForwardRef(ButtonGroup)>
+      <TimeZone />
     </div>
   </fieldset>
 </div>
@@ -518,6 +520,7 @@ exports[`TimePicker matches the snapshot when the is12hour prop is true 1`] = `
           PM
         </ForwardRef(Button)>
       </ForwardRef(ButtonGroup)>
+      <TimeZone />
     </div>
   </fieldset>
 </div>
@@ -679,6 +682,7 @@ exports[`TimePicker matches the snapshot when the is12hour prop is undefined 1`]
           value="00"
         />
       </div>
+      <TimeZone />
     </div>
   </fieldset>
 </div>

packages/components/src/date-time/time.js

@@ -16,6 +16,7 @@ import { __ } from '@wordpress/i18n';
  */
 import Button from '../button';
 import ButtonGroup from '../button-group';
+import TimeZone from './timezone';
 
 /**
  * Module Constants
@@ -277,6 +278,7 @@ class TimePicker extends Component {
 	render() {
 		const { is12Hour } = this.props;
 		const { year, minutes, hours, am } = this.state;
+
 		return (
 			<div className={ classnames( 'components-datetime__time' ) }>
 				<fieldset>
@@ -353,6 +355,8 @@ class TimePicker extends Component {
 								</Button>
 							</ButtonGroup>
 						) }
+
+						<TimeZone />
 					</div>
 				</fieldset>
 			</div>

packages/components/src/date-time/timezone.js

@@ -0,0 +1,45 @@
+/**
+ * WordPress dependencies
+ */
+import { __ } from '@wordpress/i18n';
+import { __experimentalGetSettings as getDateSettings } from '@wordpress/date';
+
+/**
+ * Internal dependencies
+ */
+import Tooltip from '../tooltip';
+
+/**
+ * Displays timezone information when user timezone is different from site timezone.
+ */
+const TimeZone = () => {
+	const { timezone } = getDateSettings();
+
+	// Convert timezone offset to hours.
+	const userTimezoneOffset = -1 * ( new Date().getTimezoneOffset() / 60 );
+
+	// System timezone and user timezone match, nothing needed.
+	// Compare as numbers because it comes over as string.
+	if ( Number( timezone.offset ) === userTimezoneOffset ) {
+		return null;
+	}
+
+	const offsetSymbol = timezone.offset >= 0 ? '+' : '';
+	const zoneAbbr =
+		'' !== timezone.abbr && isNaN( timezone.abbr )
+			? timezone.abbr
+			: `UTC${ offsetSymbol }${ timezone.offset }`;
+
+	const timezoneDetail =
+		'UTC' === timezone.string
+			? __( 'Coordinated Universal Time' )
+			: `(${ zoneAbbr }) ${ timezone.string.replace( '_', ' ' ) }`;
+
+	return (
+		<Tooltip position="top center" text={ timezoneDetail }>
+			<div className="components-datetime__timezone">{ zoneAbbr }</div>
+		</Tooltip>
+	);
+};
+
+export default TimeZone;

packages/date/src/index.js

@@ -80,7 +80,7 @@ let settings = {
 		datetime: 'F j, Y g: i a',
 		datetimeAbbreviated: 'M j, Y g: i a',
 	},
-	timezone: { offset: '0', string: '' },
+	timezone: { offset: '0', string: '', abbr: '' },
 };
 
 /**