diff --git a/phpBB/includes/functions_display.php b/phpBB/includes/functions_display.php
index 7fa32ce217..ea007b8297 100644
--- a/phpBB/includes/functions_display.php
+++ b/phpBB/includes/functions_display.php
@@ -547,11 +547,12 @@ function display_forums($root_data = '', $display_moderators = true, $return_mod
 				$last_post_subject = $last_post_subject_truncated = '';
 			}
 			$last_post_time = $user->format_date($row['forum_last_post_time']);
+			$last_post_time_rfc3339 = gmdate(DATE_RFC3339, $row['forum_last_post_time']);
 			$last_post_url = append_sid("{$phpbb_root_path}viewtopic.$phpEx", 'f=' . $row['forum_id_last_post'] . '&p=' . $row['forum_last_post_id']) . '#p' . $row['forum_last_post_id'];
 		}
 		else
 		{
-			$last_post_subject = $last_post_time = $last_post_url = $last_post_subject_truncated = '';
+			$last_post_subject = $last_post_time = $last_post_time_rfc3339 = $last_post_url = $last_post_subject_truncated = '';
 		}
 
 		// Output moderator listing ... if applicable
@@ -622,6 +623,7 @@ function display_forums($root_data = '', $display_moderators = true, $return_mod
 			'LAST_POST_SUBJECT'		=> $last_post_subject,
 			'LAST_POST_SUBJECT_TRUNCATED'	=> $last_post_subject_truncated,
 			'LAST_POST_TIME'		=> $last_post_time,
+			'LAST_POST_TIME_RFC3339'=> $last_post_time_rfc3339,
 			'LAST_POSTER'			=> get_username_string('username', $row['forum_last_poster_id'], $row['forum_last_poster_name'], $row['forum_last_poster_colour']),
 			'LAST_POSTER_COLOUR'	=> get_username_string('colour', $row['forum_last_poster_id'], $row['forum_last_poster_name'], $row['forum_last_poster_colour']),
 			'LAST_POSTER_FULL'		=> get_username_string('full', $row['forum_last_poster_id'], $row['forum_last_poster_name'], $row['forum_last_poster_colour']),
diff --git a/phpBB/search.php b/phpBB/search.php
index 4f4a14109b..8dde46f999 100644
--- a/phpBB/search.php
+++ b/phpBB/search.php
@@ -1103,9 +1103,12 @@ if ($keywords || $author || $author_id || $search_id || $submit)
 					'TOPIC_AUTHOR_COLOUR'		=> get_username_string('colour', $row['topic_poster'], $row['topic_first_poster_name'], $row['topic_first_poster_colour']),
 					'TOPIC_AUTHOR_FULL'			=> get_username_string('full', $row['topic_poster'], $row['topic_first_poster_name'], $row['topic_first_poster_colour']),
 					'FIRST_POST_TIME'			=> $user->format_date($row['topic_time']),
+					'FIRST_POST_TIME_RFC3339'	=> gmdate(DATE_RFC3339, $row['topic_time']),
 					'LAST_POST_SUBJECT'			=> $row['topic_last_post_subject'],
 					'LAST_POST_TIME'			=> $user->format_date($row['topic_last_post_time']),
+					'LAST_POST_TIME_RFC3339'	=> gmdate(DATE_RFC3339, $row['topic_last_post_time']),
 					'LAST_VIEW_TIME'			=> $user->format_date($row['topic_last_view_time']),
+					'LAST_VIEW_TIME_RFC3339'	=> gmdate(DATE_RFC3339, $row['topic_last_view_time']),
 					'LAST_POST_AUTHOR'			=> get_username_string('username', $row['topic_last_poster_id'], $row['topic_last_poster_name'], $row['topic_last_poster_colour']),
 					'LAST_POST_AUTHOR_COLOUR'	=> get_username_string('colour', $row['topic_last_poster_id'], $row['topic_last_poster_name'], $row['topic_last_poster_colour']),
 					'LAST_POST_AUTHOR_FULL'		=> get_username_string('full', $row['topic_last_poster_id'], $row['topic_last_poster_name'], $row['topic_last_poster_colour']),
diff --git a/phpBB/styles/prosilver/template/forumlist_body.html b/phpBB/styles/prosilver/template/forumlist_body.html
index a1e60b1b4d..00c104f06c 100644
--- a/phpBB/styles/prosilver/template/forumlist_body.html
+++ b/phpBB/styles/prosilver/template/forumlist_body.html
@@ -105,7 +105,7 @@
 										<i class="icon fa-external-link-square fa-fw icon-lightgray icon-md" aria-hidden="true"></i><span class="sr-only">{L_VIEW_LATEST_POST}</span>
 									</a>
 								<!-- ENDIF -->
-								<br />{forumrow.LAST_POST_TIME}
+								<br /><time datetime="{forumrow.LAST_POST_TIME_RFC3339}">{forumrow.LAST_POST_TIME}</time>
 							<!-- ELSE -->
 							{% if forumrow.U_UNAPPROVED_TOPICS %}
 								{{ lang('TOPIC_UNAPPROVED_FORUM', forumrow.TOPICS) }}
diff --git a/phpBB/styles/prosilver/template/search_results.html b/phpBB/styles/prosilver/template/search_results.html
index 391afa4d7f..9ee13a4224 100644
--- a/phpBB/styles/prosilver/template/search_results.html
+++ b/phpBB/styles/prosilver/template/search_results.html
@@ -108,7 +108,7 @@
 
 							<!-- IF not S_IS_BOT -->
 								<div class="responsive-show" style="display: none;">
-									{L_LAST_POST} {L_POST_BY_AUTHOR} <!-- EVENT search_results_last_post_author_username_prepend -->{searchresults.LAST_POST_AUTHOR_FULL}<!-- EVENT search_results_last_post_author_username_append --> &laquo; <a href="{searchresults.U_LAST_POST}" title="{L_GOTO_LAST_POST}">{searchresults.LAST_POST_TIME}</a>
+									{L_LAST_POST} {L_POST_BY_AUTHOR} <!-- EVENT search_results_last_post_author_username_prepend -->{searchresults.LAST_POST_AUTHOR_FULL}<!-- EVENT search_results_last_post_author_username_append --> &laquo; <a href="{searchresults.U_LAST_POST}" title="{L_GOTO_LAST_POST}"><time datetime="{searchresults.LAST_POST_TIME_RFC3339}">{searchresults.LAST_POST_TIME}</time></a>
 									<br />{L_POSTED} {L_IN} <a href="{searchresults.U_VIEW_FORUM}">{searchresults.FORUM_TITLE}</a>
 								</div>
 							<!-- IF searchresults.TOPIC_REPLIES --><span class="responsive-show left-box" style="display: none;">{L_REPLIES}{L_COLON} <strong>{searchresults.TOPIC_REPLIES}</strong></span><!-- ENDIF -->
@@ -118,7 +118,7 @@
 								<!-- IF searchresults.S_HAS_POLL --><i class="icon fa-bar-chart fa-fw" aria-hidden="true"></i><!-- ENDIF -->
 								<!-- IF searchresults.ATTACH_ICON_IMG --><i class="icon fa-paperclip fa-fw" aria-hidden="true"></i><!-- ENDIF -->
 								{% EVENT topiclist_row_topic_by_author_before %}
-								{L_POST_BY_AUTHOR} <!-- EVENT search_results_topic_author_username_prepend -->{searchresults.TOPIC_AUTHOR_FULL}<!-- EVENT search_results_topic_author_username_append --> &raquo; {searchresults.FIRST_POST_TIME} &raquo; {L_IN} <a href="{searchresults.U_VIEW_FORUM}">{searchresults.FORUM_TITLE}</a>
+								{L_POST_BY_AUTHOR} <!-- EVENT search_results_topic_author_username_prepend -->{searchresults.TOPIC_AUTHOR_FULL}<!-- EVENT search_results_topic_author_username_append --> &raquo; <time datetime="{searchresults.FIRST_POST_TIME_RFC3339}">{searchresults.FIRST_POST_TIME}</time> &raquo; {L_IN} <a href="{searchresults.U_VIEW_FORUM}">{searchresults.FORUM_TITLE}</a>
 								{% EVENT topiclist_row_topic_by_author_after %}
 							</div>
 
@@ -150,7 +150,7 @@
 									<i class="icon fa-external-link-square fa-fw icon-lightgray icon-md" aria-hidden="true"></i><span class="sr-only">{VIEW_LATEST_POST}</span>
 								</a>
 							<!-- ENDIF -->
-							<br />{searchresults.LAST_POST_TIME}
+							<br /><time datetime="{searchresults.LAST_POST_TIME_RFC3339}">{searchresults.LAST_POST_TIME}</time>
 						</span>
 					</dd>
 				</dl>
diff --git a/phpBB/styles/prosilver/template/viewforum_body.html b/phpBB/styles/prosilver/template/viewforum_body.html
index 9be7b5f54c..a484240c0e 100644
--- a/phpBB/styles/prosilver/template/viewforum_body.html
+++ b/phpBB/styles/prosilver/template/viewforum_body.html
@@ -187,7 +187,7 @@
 
 						<!-- IF not S_IS_BOT -->
 						<div class="responsive-show" style="display: none;">
-							{L_LAST_POST} {L_POST_BY_AUTHOR} <!-- EVENT viewforum_body_last_post_author_username_prepend -->{topicrow.LAST_POST_AUTHOR_FULL}<!-- EVENT viewforum_body_last_post_author_username_append --> &laquo; <a href="{topicrow.U_LAST_POST}" title="{L_GOTO_LAST_POST}">{topicrow.LAST_POST_TIME}</a>
+							{L_LAST_POST} {L_POST_BY_AUTHOR} <!-- EVENT viewforum_body_last_post_author_username_prepend -->{topicrow.LAST_POST_AUTHOR_FULL}<!-- EVENT viewforum_body_last_post_author_username_append --> &laquo; <a href="{topicrow.U_LAST_POST}" title="{L_GOTO_LAST_POST}"><time datetime="{topicrow.LAST_POST_TIME_RFC3339}">{topicrow.LAST_POST_TIME}</time></a>
 							<!-- IF topicrow.S_POST_GLOBAL and FORUM_ID != topicrow.FORUM_ID --><br />{L_POSTED} {L_IN} <a href="{topicrow.U_VIEW_FORUM}">{topicrow.FORUM_NAME}</a><!-- ENDIF -->
 						</div>
 							<!-- IF topicrow.REPLIES -->
@@ -199,7 +199,7 @@
 							<!-- IF topicrow.S_HAS_POLL --><i class="icon fa-bar-chart fa-fw" aria-hidden="true"></i><!-- ENDIF -->
 							<!-- IF topicrow.ATTACH_ICON_IMG --><i class="icon fa-paperclip fa-fw" aria-hidden="true"></i><!-- ENDIF -->
 							{% EVENT topiclist_row_topic_by_author_before %}
-							{L_POST_BY_AUTHOR} <!-- EVENT viewforum_body_topic_author_username_prepend -->{topicrow.TOPIC_AUTHOR_FULL}<!-- EVENT viewforum_body_topic_author_username_append --> &raquo; {topicrow.FIRST_POST_TIME}
+							{L_POST_BY_AUTHOR} <!-- EVENT viewforum_body_topic_author_username_prepend -->{topicrow.TOPIC_AUTHOR_FULL}<!-- EVENT viewforum_body_topic_author_username_append --> &raquo; <time datetime="{topicrow.FIRST_POST_TIME_RFC3339}">{topicrow.FIRST_POST_TIME}</time>
 							{% EVENT topiclist_row_topic_by_author_after %}
 							<!-- IF topicrow.S_POST_GLOBAL and FORUM_ID != topicrow.FORUM_ID --> &raquo; {L_IN} <a href="{topicrow.U_VIEW_FORUM}">{topicrow.FORUM_NAME}</a><!-- ENDIF -->
 						</div>
@@ -232,7 +232,7 @@
 								<i class="icon fa-external-link-square fa-fw icon-lightgray icon-md" aria-hidden="true"></i><span class="sr-only">{VIEW_LATEST_POST}</span>
 							</a>
 						<!-- ENDIF -->
-						<br />{topicrow.LAST_POST_TIME}
+						<br /><time datetime="{topicrow.LAST_POST_TIME_RFC3339}">{topicrow.LAST_POST_TIME}</time>
 					</span>
 				</dd>
 			</dl>
diff --git a/phpBB/styles/prosilver/template/viewtopic_body.html b/phpBB/styles/prosilver/template/viewtopic_body.html
index f17ca0b2f7..e29a2ad781 100644
--- a/phpBB/styles/prosilver/template/viewtopic_body.html
+++ b/phpBB/styles/prosilver/template/viewtopic_body.html
@@ -289,7 +289,7 @@
 						<i class="icon fa-file fa-fw <!-- IF postrow.S_UNREAD_POST -->icon-red<!-- ELSE -->icon-lightgray<!-- ENDIF --> icon-md" aria-hidden="true"></i><span class="sr-only">{postrow.MINI_POST}</span>
 					</a>
 				<!-- ENDIF -->
-				<span class="responsive-hide">{L_POST_BY_AUTHOR} <strong>{postrow.POST_AUTHOR_FULL}</strong> &raquo; </span>{postrow.POST_DATE}
+				<span class="responsive-hide">{L_POST_BY_AUTHOR} <strong>{postrow.POST_AUTHOR_FULL}</strong> &raquo; </span><time datetime="{postrow.POST_DATE_RFC3339}">{postrow.POST_DATE}</time>
 			</p>
 			<!-- EVENT viewtopic_body_postrow_post_details_after -->
 
diff --git a/phpBB/viewforum.php b/phpBB/viewforum.php
index 72c96e2d2d..0a5484cdf2 100644
--- a/phpBB/viewforum.php
+++ b/phpBB/viewforum.php
@@ -933,9 +933,12 @@ if (count($topic_list))
 			'TOPIC_AUTHOR_COLOUR'		=> get_username_string('colour', $row['topic_poster'], $row['topic_first_poster_name'], $row['topic_first_poster_colour']),
 			'TOPIC_AUTHOR_FULL'			=> get_username_string('full', $row['topic_poster'], $row['topic_first_poster_name'], $row['topic_first_poster_colour']),
 			'FIRST_POST_TIME'			=> $user->format_date($row['topic_time']),
+			'FIRST_POST_TIME_RFC3339'	=> gmdate(DATE_RFC3339, $row['topic_time']),
 			'LAST_POST_SUBJECT'			=> censor_text($row['topic_last_post_subject']),
 			'LAST_POST_TIME'			=> $user->format_date($row['topic_last_post_time']),
+			'LAST_POST_TIME_RFC3339'	=> gmdate(DATE_RFC3339, $row['topic_last_post_time']),
 			'LAST_VIEW_TIME'			=> $user->format_date($row['topic_last_view_time']),
+			'LAST_VIEW_TIME_RFC3339'	=> gmdate(DATE_RFC3339, $row['topic_last_view_time']),
 			'LAST_POST_AUTHOR'			=> get_username_string('username', $row['topic_last_poster_id'], $row['topic_last_poster_name'], $row['topic_last_poster_colour']),
 			'LAST_POST_AUTHOR_COLOUR'	=> get_username_string('colour', $row['topic_last_poster_id'], $row['topic_last_poster_name'], $row['topic_last_poster_colour']),
 			'LAST_POST_AUTHOR_FULL'		=> get_username_string('full', $row['topic_last_poster_id'], $row['topic_last_poster_name'], $row['topic_last_poster_colour']),
diff --git a/phpBB/viewtopic.php b/phpBB/viewtopic.php
index 0c2be8c52e..dadbe9a06c 100644
--- a/phpBB/viewtopic.php
+++ b/phpBB/viewtopic.php
@@ -2044,6 +2044,7 @@ for ($i = 0, $end = count($post_list); $i < $end; ++$i)
 		'CONTACT_USER'		=> $user_cache[$poster_id]['contact_user'],
 
 		'POST_DATE'			=> $user->format_date($row['post_time'], false, ($view == 'print') ? true : false),
+		'POST_DATE_RFC3339'	=> gmdate(DATE_RFC3339, $row['post_time']),
 		'POST_SUBJECT'		=> $row['post_subject'],
 		'MESSAGE'			=> $message,
 		'SIGNATURE'			=> ($row['enable_sig']) ? $user_cache[$poster_id]['sig'] : '',