use strict; use warnings;
use feature qw/ say state /;
use DateTime::Format::Strptime;

for ( <DATA> ) {
    chomp;
    say sprintf '%-24s: %s', $_, validate( $_ ) ? 'OK' : 'Not OK';
}

sub validate {
    state $parser = DateTime::Format::Strptime->new(
        pattern => '%F %T.%3N',
        on_error => 'croak',
    );

    return eval { $parser->parse_datetime( @_ ); 1 };
}

__DATA__
2017-01-29 11:30:07.370
2017-01-29 11:30:07.000
2017-01-32 11:30:07.370
2017-01-29 11:30:07
foo bar

##</code><code>##

my $str = '2017-01-29 11:30:07.370';
$parser = DateTime::Format::Strptime->new( pattern => '%F %T.%3N' );

if ( my $dt = $parser->parse_datetime( $str ) ) {
    say "Interestingly, $str falls on a " . $dt->day_name;
} else {
    say "$str is not a valid date";
}