diff --git a/wp-includes/comment.php b/wp-includes/comment.php
index 16bd29ea1e..72fef8bab1 100644
--- a/wp-includes/comment.php
+++ b/wp-includes/comment.php
@@ -280,7 +280,7 @@ class WP_Comment_Query {
 		$key = md5( serialize( compact(array_keys($defaults)) )  );
 		$last_changed = wp_cache_get( 'last_changed', 'comment' );
 		if ( ! $last_changed ) {
-			$last_changed = microtime();
+			$last_changed = microtime( true );
 			wp_cache_set( 'last_changed', $last_changed, 'comment' );
 		}
 		$cache_key = "get_comments:$key:$last_changed";
@@ -1560,7 +1560,7 @@ function wp_insert_comment($commentdata) {
 	 */
 	do_action( 'wp_insert_comment', $id, $comment );
 
-	wp_cache_set( 'last_changed', microtime(), 'comment' );
+	wp_cache_set( 'last_changed', microtime( true ), 'comment' );
 
 	return $id;
 }
@@ -2360,7 +2360,7 @@ function clean_comment_cache($ids) {
 	foreach ( (array) $ids as $id )
 		wp_cache_delete($id, 'comment');
 
-	wp_cache_set( 'last_changed', microtime(), 'comment' );
+	wp_cache_set( 'last_changed', microtime( true ), 'comment' );
 }
 
 /**
diff --git a/wp-includes/general-template.php b/wp-includes/general-template.php
index 642aa722cf..ab4ad61c25 100644
--- a/wp-includes/general-template.php
+++ b/wp-includes/general-template.php
@@ -985,7 +985,7 @@ function wp_get_archives($args = '') {
 
 	$last_changed = wp_cache_get( 'last_changed', 'posts' );
 	if ( ! $last_changed ) {
-		$last_changed = microtime();
+		$last_changed = microtime( true );
 		wp_cache_set( 'last_changed', $last_changed, 'posts' );
 	}
 
diff --git a/wp-includes/post.php b/wp-includes/post.php
index 02cc7d5a5e..f6f10f197c 100644
--- a/wp-includes/post.php
+++ b/wp-includes/post.php
@@ -3749,7 +3749,7 @@ function get_pages( $args = array() ) {
 	$key = md5( serialize( compact(array_keys($defaults)) ) );
 	$last_changed = wp_cache_get( 'last_changed', 'posts' );
 	if ( ! $last_changed ) {
-		$last_changed = microtime();
+		$last_changed = microtime( true );
 		wp_cache_set( 'last_changed', $last_changed, 'posts' );
 	}
 
@@ -4763,7 +4763,7 @@ function clean_post_cache( $post ) {
 		do_action( 'clean_page_cache', $post->ID );
 	}
 
-	wp_cache_set( 'last_changed', microtime(), 'posts' );
+	wp_cache_set( 'last_changed', microtime( true ), 'posts' );
 }
 
 /**
diff --git a/wp-includes/taxonomy.php b/wp-includes/taxonomy.php
index b2336c8a59..34f7900426 100644
--- a/wp-includes/taxonomy.php
+++ b/wp-includes/taxonomy.php
@@ -1313,7 +1313,7 @@ function get_terms($taxonomies, $args = '') {
 	$key = md5( serialize( compact(array_keys($defaults)) ) . serialize( $taxonomies ) . $filter_key );
 	$last_changed = wp_cache_get( 'last_changed', 'terms' );
 	if ( ! $last_changed ) {
-		$last_changed = microtime();
+		$last_changed = microtime( true );
 		wp_cache_set( 'last_changed', $last_changed, 'terms' );
 	}
 	$cache_key = "get_terms:$key:$last_changed";
@@ -2814,7 +2814,7 @@ function clean_term_cache($ids, $taxonomy = '', $clean_taxonomy = true) {
 		set_taxonomy_last_changed( $taxonomy );
 	}
 
-	wp_cache_set( 'last_changed', microtime(), 'terms' );
+	wp_cache_set( 'last_changed', microtime( true ), 'terms' );
 }
 
 /**