Date/Time: Use delta comparison in get_gmt_from_date() tests to avoid race conditions.

Follow-up to [35284].

Props keesiemeijer.
Merges [41920] to the 4.7 branch.
See #38815.

git-svn-id: https://develop.svn.wordpress.org/branches/4.7@51613 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

tests/phpunit/tests/formatting/date.php

@@ -81,16 +81,16 @@ function test_get_gmt_from_date_short_date() {
 	function test_get_gmt_from_date_string_date() {
 		update_option( 'timezone_string', 'Europe/London' );
 		$local = 'now';
-		$gmt = gmdate( 'Y-m-d H:i:s', strtotime( 'now' ) );
-		$this->assertEquals( $gmt, get_gmt_from_date( $local ) );
+		$gmt = gmdate( 'Y-m-d H:i:s' );
+		$this->assertEquals( strtotime( $gmt ), strtotime( get_gmt_from_date( $local ) ), 'The dates should be equal', 2 );
 	}
 
 	/**
 	 * @ticket 34279
 	 */
 	function test_get_gmt_from_date_string_date_no_timezone() {
 		$local = 'now';
-		$gmt = gmdate( 'Y-m-d H:i:s', strtotime( 'now' ) );
-		$this->assertEquals( $gmt, get_gmt_from_date( $local ) );
+		$gmt = gmdate( 'Y-m-d H:i:s' );
+		$this->assertEquals( strtotime( $gmt ), strtotime( get_gmt_from_date( $local ) ), 'The dates should be equal', 2 );
 	}
 }