Hello @tahasozgen,
Will start with the timestamp you state in your question. Just want you to understand that is not a valid timestamp. That is the display format chosen by your for the timestamp. The timestamp is actually stored in the DB as:
YYYY-MM-DD HH:MM:SS
I point this out to help understand this SQL.
So to extract just the date in the format you want using a data field:
Select TO_CHAR(YOUR_TIMESTAMP, 'DD.MM.YY' ) AS "A_NAME" from "YOUR_TABLE"
To extract just the date in the format you want using a literal:
Select TO_CHAR(cast('2018-09-30 02:18' AS TIMESTAMP), 'DD.MM.YY' ) AS "A_NAME" from "YOUR_TABLE"
Also, the reason for asking for the type of DB used is that SQL can differ in databases. Understand HSQLDB is old & is in the process of being replaced with Firebird 3 embedded.