Portolio's Target Start and Target End fields can be added to a JQL search. When exporting the search to a CSV file, both fields are exported in a timestamp format (i.e. 27/Sep/18 12:00 AM) using the system date field of Jira. However, both fields are date-only fields in the UI (the user doesn't have the option to pick the time, only the date).

In other words, the UI shows the date as UTC (date only) and exports it as the system timezone used by Jira (as date-time). This shifts the date into the previous day and causes confusion. 

JQL Of Portfolio Dates

CSV Export

Issue key,Issue id,Parent id,Status,Created,Updated,Custom field (rm.jpo.plan.common.baselineStart),Custom field (rm.jpo.plan.common.baselineEnd)

ANDY-3,10102,,To Do,11/Jun/19 12:57 PM,11/Jun/19 1:54 PM,17/Jun/19 7:00 PM,30/Jun/19 7:00 PM
ANDY-2,10101,,To Do,11/Jun/19 12:57 PM,11/Jun/19 1:54 PM,17/Jun/19 7:00 PM,30/Jun/19 7:00 PM
ANDY-1,10100,,To Do,11/Jun/19 12:57 PM,11/Jun/19 1:54 PM,17/Jun/19 7:00 PM,30/Jun/19 7:00 PM

In this specific example, Central Daylight Time (CDT) is 5 hours behind of Universal Time Coordinated (UTC), so the export is 5 hours behind, changing the date that is displayed in the UI and causing confusion.

Expected behaviour.
Only the date field should be exported to CSV without any shifts in hours/timezones.