[RogerHYang]

Summary

• define overflow behavior for extreme date, duration, conversion, and serialization operations
• correct leap-day boundaries, week truncation, wide-year and negative-offset formatting, and ancient-time blob round trips
• add focused boundary regression coverage and update the documented week-truncation result

Test plan

• Time C tests under AddressSanitizer and UndefinedBehaviorSanitizer
• Duration C tests under AddressSanitizer and UndefinedBehaviorSanitizer
• Time SQL suite against the rebuilt extension
• 1,000,000 libFuzzer inputs under ASan/UBSan

[RogerHYang]

Additional fuzz validation: I ran this time-library harness for 100,000,000 libFuzzer executions across eight workers under ASan and UBSan. It exercises parsing, blobs, arbitrary date fields, arithmetic, rounding, formatting, and round-trip invariants using independent reference oracles.

All jobs completed in about 53 seconds wall-clock with no crashes, sanitizer findings, or oracle failures.