$ TZ=America/New_York perl -e'
    use strict;
    use warnings;

    use DateTime      qw( );
    use POSIX         qw( strftime );
    use Time::Piece   qw( localtime );
    use Time::Seconds qw( ONE_HOUR );

    my $epoch = 1583683200;  # 2020-03-08T12:00:00

    CORE::say
       for
          DateTime->from_epoch( epoch => $epoch, time_zone => $ENV{TZ} )->subtract( hours => 12 ),
          strftime("%FT%T", localtime($epoch - 12*60*60)),
          ( localtime($epoch) - 12*ONE_HOUR )->strftime("%FT%T");
'
2020-03-07T23:00:00
2020-03-07T23:00:00
2020-03-07T23:00:00