The runner's Node carries English-only ICU and formats en-GB as en-US
("Oct 5", "EDT"); browsers carry full ICU. What #38 guards is which day
and which hour, so that is what the test checks.
Refs #38
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015pkwBsR54NRmZyU4QVhvfj