diff --git a/inc/template-tags.php b/inc/template-tags.php
index 056291d5..769c6ac1 100644
--- a/inc/template-tags.php
+++ b/inc/template-tags.php
@@ -18,9 +18,9 @@ if ( ! function_exists( '_s_posted_on' ) ) :
 		}
 
 		$time_string = sprintf( $time_string,
-			esc_attr( get_the_date( 'c' ) ),
+			esc_attr( get_the_date( DATE_W3C ) ),
 			esc_html( get_the_date() ),
-			esc_attr( get_the_modified_date( 'c' ) ),
+			esc_attr( get_the_modified_date( DATE_W3C ) ),
 			esc_html( get_the_modified_date() )
 		);