Ravi Kiran Katha

<p>WordPress has a site-level timezone setting configured from the admin back-end. All dates and times displayed on the front-end are typically displayed in this timezone.</p>
<p>This plugin enables the display of dates/times in the front-end using the browser’s timezone. This is done by overriding the WordPress’s <strong>‘timezone_string’</strong> and <strong>‘gmt_offset’</strong> options to match the user’s timezone <strong>for the duration of a particular request</strong><br />
<strong>ONLY on the front-end interface</strong>.</p>
<h4>Browser Timezone Detection</h4>
<p>The browser’s timezone is detected using one of the following two methods</p>
<ol>
<li><a href="http://pellepim.bitbucket.org/jstz/" rel="nofollow ugc">jsTimezoneDetect</a> (default)</li>
<li><a href="http://caniuse.com/geolocation" rel="nofollow ugc">HTML5 Geolocation API</a> and <a href="https://developers.google.com/maps/documentation/timezone" rel="nofollow ugc">Google Timezone API</a></li>
</ol>
<p><strong>jsTimezoneDetect (default)</strong><br />
    This is the default timezone detection mechanism. Please refer to the script <a href="http://pellepim.bitbucket.org/jstz/" rel="nofollow ugc">home page</a><br />
for the compatibility and other notes</p>
<p><strong>HTML5 Geolocation API</strong><br />
    Detects the current geo-location using <em><a href="http://caniuse.com/geolocation" rel="nofollow ugc">navigator.geolocation.getCurrentPosition</a></em>. The location thus detected will be sent to the <a href="https://developers.google.com/maps/documentation/timezone" rel="nofollow ugc">Google Timezone API</a><br />
which returns the timezone id – similar to “Asia/Kolkata”.</p>
<p>This method requires you to</p>
<ul>
<li>Enable the “Google Timezone API” option on the plugin options page</li>
<li>Specify a valid <a href="https://developers.google.com/maps/documentation/timezone/get-api-key" rel="nofollow ugc">Google API Key</a>
<ul>
<li>The key should be a browser key</li>
<li>The “Accepted HTTP Referrers” should include the domain name used by the hosting wordpress site or left blank to allow all referrers</li>
</ul>
</li>
</ul>
<p>If the required options for the usage of Google Timezone API are not met, the detection mechanism falls back to the default one.</p>
<h4>Post Timezone Detection</h4>
<ul>
<li>If the browser’s timezone id is not detected successfully, everything else behaves as if this plugin is not installed.</li>
<li>If the browser’s timezone id is detected, the following actions take place
<ul>
<li>A cookie will be set in the browser, based on the cookie options specified on the plugin options page</li>
<li>If a cookie already exists previously with the same id, no action is taken</li>
<li>If a cookie doesn’t already exist previously or exists with a different timezone id, then a <em>window.reload</em> is triggered to refresh the page so that the dates/times on the page are updated</li>
</ul>
</li>
</ul>
<h4>EventON Hook</h4>
<p>This plugin provides a feature to hook into the EventON plugin. When enabled, all EventON dates/times are updated to reflect the browser’s timezone.</p>
<h4>Shortcodes</h4>
<p>This plugin defines the below shortcodes</p>
<ol>
<li>[wp_user_timezone_id] => Returns the timezone id of the browser or <em>null</em> if not available.</li>
<li>[wp_user_timezone_offset] => Returns the timezone’s gmt offset in hours of the browser or <em>null</em> if not available.</li>
</ol>
<h4>Options</h4>
<p>This plugin defines the below options to retrieve the original timezone_string and gmt_offset defined at the site level</p>
<ol>
<li>get_option( ‘site_timezone_string’ ) => Returns the original timezone_string option for the site</li>
<li>get_option( ‘site_gmt_offset’ ) => Returns the original gmt_offset option for the site</li>
</ol>
<h4>Actions/Hooks</h4>
<p>This plugin defines the below filters/hooks</p>
<ol>
<li>apply_filters( ‘wp_user_timezone_id’, $tz_id ) => Allows you to override the timezone string determined by the plugin. This filter can be used to apply user’s timezone preference. If any plugin or wordpress core implements a feature to accept and store user’s preferred timezone, the ‘wp_user_timezone_id’ can be used to apply that timezone value to the front-end. Reference: <a href="https://core.trac.wordpress.org/ticket/18146" rel="nofollow ugc">Add user-level timezone setting</a>).</li>
</ol>
<h4>Admin Backend Dates/Times</h4>
<p><strong>Important: The admin back-end is not modified by this plugin. All dates/times displayed in the back-end are still in the original timezone specified by the WordPress General Settings.</strong></p>


WP User Timezone

Magnificent

WP User Timezone displays the front-end dates & times in the browser's local timezone without actually modifying your database.

Antonio D.

Daniil Zhitnitskii

<p>This plugin provides network administrators ability to set same time zone over all blogs in multisite installation in one click, and also it restricts changes of timezone from local blogs settings.</p>
<p>*Based on: https://premium.wpmudev.org/forums/topic/set-default-timezone-for-new-blogs-in-the-network</p>
<p><strong>Only works with multisite installation!</strong></p>
<p>Gutenberg: compatible!</p>
<h3>Disclaimers</h3>
<p>The Simple default timezone plugin is supplied “as is” and all use is at your own risk.</p>


Simple default timezone

As Super Administrator, you can set the (default) timezone for all blogs.

WP User Timezone vs Simple default timezone