After I have not been able to find a solution that would be easy to implement inside of NiFi, I've written a small perl (yuk) script that can be used to adjust timestamps in a CSV file to be in ISO8601 format.  Maybe it is useful to someone else: #!/bin/perl -w # This perl script adds timezone information to timestamps without a # timezone. All timestamps in the input file that follow the format # "YYYY-MM-DD HH:MM:SS" are converted to ISO8601 timestamps. use strict; use DateTime::Format::Strptime; my $time_zone = 'Europe/Amsterdam'; my $parser = DateTime::Format::Strptime->new( pattern => '%Y-%m-%d %T', time_zone => $time_zone ); my $printer = DateTime::Format::Strptime->new( pattern => '%FT%T%z', time_zone => $time_zone ); while (<>) { s/(?<=")(\d\d\d\d-\d\d-\d\d \d\d:\d\d:\d\d)(?=")/ my $dt = $parser->parse_datetime($1); $printer->format_datetime($dt); /ge; print; }   ... View more