Dataset export to Excel datetime conversion issue

Sorry I couldnt get as required.

Table JSON is converted to dataset and I used system.dataset.formatDates as suggested. But no conversion. I still get in unix milliseconds timestamp.

data = self.parent.parent.getChild("TableConsumption").props.data

# TableEXPORTFIELDCHOOSER is a custom made table for users to choose the columns and order of column to export.
tablefieldds = self.getSibling("TableEXPORTFIELDCHOOSER").props.data
sorttablefieldds = system.dataset.sort(tablefieldds, 2)

#Get the chosen columns	
tablefieldheader = []
for row in range(sorttablefieldds.rowCount):
	if sorttablefieldds.getValueAt(row, "CHOOSE") == True:
		tablefieldheader.append(sorttablefieldds.getValueAt(row, "COLUMNS"))
	
system.perspective.print(tablefieldheader)
system.perspective.print(len(tablefieldheader))

tpc = self.parent.parent.getChild("TableConsumption").props.columns
newheader = []

#Get the field name for columns		
for title in range(len(tablefieldheader)):
	for row in range(len(tpc)):
		if tablefieldheader[title] == tpc[row]["header"]["title"] :
			tpcfield = tpc[row]["field"]
			newheader.append(tpcfield)
system.perspective.print(newheader)
system.perspective.print(len(newheader))

#convert JSON table output to dataset	
datasetData = []
for row in range(len(data)):	
	rowData = []
	for col in range(len(newheader)):
		cell = data[row][newheader[col]]
		if hasattr(cell, 'value'):
			rowData.append(cell.value)
		else:
			rowData.append(cell)
	#system.perspective.print(rowData)
	datasetData.append(rowData)

#export to excel	
finalDataset = system.dataset.toDataSet(tablefieldheader,datasetData)
formatdateds = system.dataset.formatDates(finalDataset, "dd-mm-yyyy")
XLSFormat = system.dataset.dataSetToExcel(True,[formatdateds], True)
timenow = system.date.format(system.date.now(), 'dd_MM_yyyy_HH_mm')
filename = 'T2_SHIFTPARAMS_' + timenow + '.xls'
system.perspective.download(filename,XLSFormat)