operators <= (Less than or equal to) and > (greater than) are not working properly with dates

When I run the query 'created <= '2015-09-04' it does not include any JIRAs created on 2015-09-04. Less than or equal to is acting like less than, when it should be including the specified date.

When I run the query 'created > '2015-09-03' it is including any JIRAs created on 2015-09-03. Greater than is acting like greater than or equal to, when it should be excluding the specified date.

This is affecting all of our reporting that we run in JIRA