[mattasplund]

Summary

• Parse English HTTP date month and weekday names without relying on the process locale.
• Keep support for HTTP dates with or without seconds and validate parsed fields.
• Add datetime regression coverage for the reported GMT date format.

This prevents TDateTime from asserting on valid HTTP dates when LC_TIME uses a non-English locale.

Tests

• cmake --build build-date --target datetime_test --parallel 4
• ctest --test-dir build-date --output-on-failure -R ^datetime$ (passed)