The date locale/format are different when viewing a report versus viewing the report output as a result of a schedule report. How to set the Jasper date locale when scheduling a report?
When scheduling a reporting, in the Output Options tab, the locale settings to be used for generating the report can be set. Here's an explanation on the same from Jasper Server documentation (https://community.jaspersoft.com/documentation/tibco-jasperreports-server-user-guide/v71/setting-output-options)
Output Locale – The locale settings for generating the report.
The report must support locales, for example a report based on a Domain with language bundles (see Security and Locale Information for a Domain).