I've created an extremely difficult regex challenge focusing on two complex pattern types that often trip up even experienced developers: email address validation and ISO-8601 timestamp formats. 

The challenge includes extremely varied formats of valid emails (with special characters, IP literals, multiple subdomains, and non-standard TLDs) alongside nearly-valid but invalid entries. The timestamps include multiple ISO-8601 variations including timezone offsets, fractional seconds, ordinal date... (truncated)