Docs: Add description for is_day().

Props webdevmattcrom.
Fixes #42784.

Built from https://develop.svn.wordpress.org/trunk@42355


git-svn-id: http://core.svn.wordpress.org/trunk@42184 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/query.php

@@ -323,6 +323,8 @@ function is_date() {
 /**
  * Is the query for an existing day archive?
  *
+ * A conditional check to test whether the page is a date-based archive page displaying posts for the current day.
+ *
  * @since 1.5.0
  *
  * @global WP_Query $wp_query Global WP_Query instance.

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.0-alpha-42354';
+$wp_version = '5.0-alpha-42355';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.