Solution : https://service.sap.com/sap/support/notes/1379814 (SAP Service marketplace login required)
Key words : 
date type cnca_utc_date    exceptions      cntl_error, call method cl_gui_cfw=>flush, calendar controls focused date, terms calendar control, latest focused date, methods get_ctl_calendar_focused_date    exporting, focused date, selected date, method 'get_ctl_calendar_focused_date', method returns
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