ReportLab - Metadata, CreationDate and ModificationDate

How can I change metadata fields, CreationDate and ModificationDate, when I create a pdf with Reportlab?

Take a look at where modification and creation dates are set:

D['ModDate'] = D["CreationDate"] = \
             Date(ts=document._timeStamp,dateFormatter=self._dateFormatter)
# ...
return PDFDictionary(D).format(document)

Basically, metadata is a dictionary saved at the end of binary string, start of string is file contents (document).

Inside Reportlab the workflow you ask about can be:

• create canvas
• draw something on it
• get document from canvas
• create PDFDictionary with artificial mod and create dates
• format document with PDFDictionary
• save to file

Change metadata of pdf file with pypdf also attempts similar goal.