The TIMESTAMP_FORMAT option sets the format retrieved from the database. The tool used to display the results may format that data in a different way.
In DBISQL 17, the default is to display the date using the OS regional settings. To display the settings as defined on the server, you have to:
1. go to Tools | Options
2. select the SQL Anywhere category
3. select "on database server" from the Format Dates and Times dropdown.
This format setting does not change the underlying data stored just how it gets displayed.