Default date format changed after PO Print Preview

Currently, my user id default date format is 2 MM/DD/YYYY

My PO Line Item shows my delivery date to be 06/14/2016, which is correct.

Then i'll print preview my PO. But my PO shows my delivery date to be 14/06/2016, which is wrong. But this can be change as it is Z form

Then when i exit my Print Preview, my PO Line Item delivery date will become 14.06.2016 and not the initial 6/14/2016

Only after i /nme23n, then only it shows back 6/14/2016

Does my PO Print Preview which is a Z-form will overwrites my SAP Default date format?

But then again, where do the DD.MM.YYYY format come from?