DateTime::Format::W3CDTF Nanosecond Validation Bug

README.md

DateTime::Format::W3CDTF Nanosecond Validation Bug

DateTime::Format::W3CDTF fails to parse datetime strings containing fractional seconds when used with Specio 0.50+.

DateTime 1.66 requires Specio 0.50+, which has stricter integer validation. This exposes a bug in DateTime::Format::W3CDTF that was previously hidden.

How to Run

# DateTime 1.65 + Specio 0.49 (works)
docker build -f Dockerfile.1.65 -t datetime-bug:1.65 .
docker run --rm datetime-bug:1.65

# DateTime 1.66 + Specio 0.50+ (fails)
docker build -f Dockerfile.1.66 -t datetime-bug:1.66 .
docker run --rm datetime-bug:1.66

Results

DateTime 1.65 + Specio 0.49 (Success)

DateTime version: 1.65
DateTime::Format::W3CDTF version: 0.08

Parsing: 2026-02-20T14:59:45.268Z
Success: 2026-02-20T14:59:45

DateTime 1.66 + Specio 0.50+ (Failure)

DateTime version: 1.66
DateTime::Format::W3CDTF version: 0.08

Parsing: 2026-02-20T14:59:45.268Z
Error: Validation failed for type named Nanosecond ... with value 268000000

Root Cause

• Specio 0.50 introduced stricter validation for integer types (PositiveOrZeroInt)
• DateTime::Format::W3CDTF passes nanoseconds as a floating-point number instead of an integer
• DateTime 1.66 requires Specio 0.50+, so users upgrading to DateTime 1.66 will encounter this bug

Problem Location

DateTime::Format::W3CDTF line 101:

# Current code (produces float)
$p{nanosecond} = $p{fraction} * 1_000_000_000;

# Fix (produces integer)
use POSIX qw(floor);
$p{nanosecond} = floor($p{fraction} * 1_000_000_000);

Related

• https://github.com/houseabsolute/DateTime.pm
• https://github.com/kasei/datetime-format-w3cdtf

Dockerfile.1.65

FROM perl:5.38

# Use Specio 0.49 (Specio 0.50+ has stricter integer validation)
RUN cpanm --notest Specio@0.49 && cpanm --notest DateTime@1.65 DateTime::Format::W3CDTF

WORKDIR /app
COPY test.pl .

CMD ["perl", "test.pl"]

Dockerfile.1.66

FROM perl:5.38

# DateTime 1.66 requires Specio 0.50+ (stricter integer validation)
RUN cpanm --notest DateTime@1.66 DateTime::Format::W3CDTF

WORKDIR /app
COPY test.pl .

CMD ["perl", "test.pl"]

test.pl

#!/usr/bin/env perl
use strict;
use warnings;
use DateTime;
use DateTime::Format::W3CDTF;

print "DateTime version: $DateTime::VERSION\n";
print "DateTime::Format::W3CDTF version: $DateTime::Format::W3CDTF::VERSION\n";
print "\n";

my $input = '2026-02-20T14:59:45.268Z';
print "Parsing: $input\n";

eval {
    my $dt = DateTime::Format::W3CDTF->parse_datetime($input);
    print "Success: $dt\n";
};
if ($@) {
    print "Error: $@\n";
}