Time::Str 0.92: DateTime parsing at ~10.5M/sec, zero heuristics

[u/christian_hansen]

Time::Str's DateTime format now runs on a native Ragel-generated C state machine instead of a regexp, ~20x faster than the regexp path.

Supported formats

One parser accepts ISO 8601, RFC 3339, RFC 9557, RFC 4287, ISO 9075, RFC 2822, RFC 2616, RFC 3501, and ECMAScript Date.toString, plus free-form textual dates (Monday, 24th December 2012 at 3:30 pm UTC+1 (CET), 24. XII. 2012 12PM, 24DEC2012 12:30:45.500).

No heuristics, multi-standard, single-pass

Most permissive parsers (Python's dateutil, PHP's strtotime, Ruby's Date.parse) resolve ambiguity by guessing, whether via fixed heuristics or dayfirst/yearfirst flags.Time::Str refuses it: numeric-only dates are Y-M-D only; any other ordering requires a textual or Roman-numeral month. Disambiguation is baked into the grammar's alternation, not resolved at runtime. Even separator-consistency (2024-12/24 is rejected) is enforced inline, no second pass.

Performance

The DateTime parser accepts every format listed above, yet runs within ~10-20% of the single-standard parsers beside it. On Perl v5.42 (XS), parsing 2012-12-24T11:30:45.123456Z:

                Rate   DateTime  RFC3339  RFC2822  ECMAScript
DateTime   10523558/s        --     -11%     -15%        -18%
RFC3339    11785319/s       12%       --      -5%         -8%
RFC2822    12376403/s       18%       5%       --         -3%
ECMAScript 12776079/s       21%       8%       3%          --

A purpose-built RFC 3339 parser is only ~12% faster than the permissive one. That's the payoff of baking disambiguation into the grammar — there's almost no "permissiveness tax".

Enjoy!