Export data grouped by visitId

Hello everyone,

couldn´t find anything on this topic so here is my problem.
I try to export data from piwik for cluster analysis. I want the data to be grouped by the visit ID.
I run this command for the export:


My problem is the date of the visit. With serverTimePretty i only get times like 23:55 ±4 minutes. This can´t be true and i don´t want the time, i want the day an month.
Can anyone help me with that?