From 1985d1ee0c136ca17fe9afa53ec23f3700e98bba Mon Sep 17 00:00:00 2001
From: Jochen Staerk <jstaerk@usegroup.de>
Date: Thu, 21 Mar 2019 16:58:24 +0100
Subject: [PATCH] support two digit years

With this change you can use two digit years, i.e. $fileHandler->setFilenameFormat('{date}_{filename}', 'y-m-d'); for 19-03-21
---
 src/Monolog/Handler/RotatingFileHandler.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Monolog/Handler/RotatingFileHandler.php b/src/Monolog/Handler/RotatingFileHandler.php
index 3e2810ba..c1ff25b5 100644
--- a/src/Monolog/Handler/RotatingFileHandler.php
+++ b/src/Monolog/Handler/RotatingFileHandler.php
@@ -81,7 +81,7 @@ class RotatingFileHandler extends StreamHandler
 
     public function setFilenameFormat(string $filenameFormat, string $dateFormat): self
     {
-        if (!preg_match('{^Y(([/_.-]?m)([/_.-]?d)?)?$}', $dateFormat)) {
+        if (!preg_match('{^[Yy](([/_.-]?m)([/_.-]?d)?)?$}', $dateFormat)) {
             throw new InvalidArgumentException(
                 'Invalid date format - format must be one of '.
                 'RotatingFileHandler::FILE_PER_DAY ("Y-m-d"), RotatingFileHandler::FILE_PER_MONTH ("Y-m") '.