This PR was merged into the 2.1 branch.Commits-------81967f6 [Form] Fixed failing tests for DateTimeToStringTransformer.Discussion----------[Form] Fixed failing tests for DateTimeToStringTransformerBug fix: noFeature addition: noBackwards compatibility break: noSymfony2 tests pass: yesFixes the following tickets: -Todo: -License of the code: MITDocumentation PR: -Tests were only failing at the end of the month. Since February was used in the test cases, date was being moved to the next month (February has less days than other months).If a day is not passed, \DateTime's constructor will set it to the first day of the month:```phpvar_dump(new \DateTime('2010-02'));object(DateTime)#1 (3) {  ["date"]=>  string(19) "2010-02-01 00:00:00"  ["timezone_type"]=>  int(3)  ["timezone"]=>  string(13) "Europe/London"}```\DateTime is used in the test assertions.However, DateTimeToStringTransformer::reverseTransform() uses \DateTime::createFromFormat(), which sets a missing day to the current day:```phpvar_dump(\DateTime::createFromFormat("Y-m", '2010-02'));object(DateTime)#1 (3) {  ["date"]=>  string(19) "2010-03-01 20:09:26"  ["timezone_type"]=>  int(3)  ["timezone"]=>  string(13) "Europe/London"}```I changed the date in the test case to avoid failures. If we need to be sure that month's not going to be changed, I'll update my PR.