How to handle Date Pickers

If you right click on the calendar GUI you will be able to review the HTML and search for your date like in a web table.

How to handle Web Tables | Katalon Docs

You may have to create several objects to represent parts of the calendar GUI, such as the right and left arrows, the year and the month name (e.g. SEP).

Secondly, you can parse a given date into year, month and date and set it on your GUI.

I put a sample of this on this forum some time back. Note that the HTML may likely be different but you should be able to adjust it to your calendar GUI.