You should be aware of the Reporting Services
uses the locale settings based on the report server operating system.
And to can show date time format based on the SharePoint regional settings
, you will need to set The Language property
on a report which determines the default formats for displaying report data like date, currency, or number values.
To set the The Language property
for a report
In Design view, click outside the report design surface to select the report.
In the Properties pane, for the Language property, type or select the language that you want to use for the report.
For more details check Set the Locale for a Report (Reporting Services)
Note: you also should make sure that
If you are using SQL Server 2012 SP1
and you have configured the SSRS in integrated mode and the regional setting is not reflected to your date time parameter , in this case , you will need to install Cumulative Update 3 for SQL Server 2012 SP1
If you are using SQL Server 2012
you will need to install Cumulative update 5 for SQL Server 2012
Note:
To get the build number of your SQL version check Get the build number of the latest Cumulative Update / Service Pack that has been installed in SQL Server
To install suitable Cumulative update check : FIX: The DateTime parameter is not displayed by using the regional setting format of a SharePoint website in SSRS 2012