2026-03-31 | 🕐 The Tomorrow Reflection Bug ⏰
🐛 The Problem
🌅 At 7:30 PM Pacific on March 31st, a daily reflection for April 1st already existed in the Obsidian vault. The reflection system is supposed to create notes only for today, never for future dates.
🕐 The root cause is a timezone mismatch. When a Copilot agent created an AI blog post at 7:30 PM Pacific, the server clock read April 1st in UTC. The filename was stamped with the UTC date instead of the Pacific date.
🔍 Root Cause
🗂️ The backfill-blog-images task updates navigation links on AI blog posts, then records those changes as update links on the corresponding day’s reflection. To figure out which day’s reflection to update, it calls extractPostDate, which reads the date straight from the filename.
📁 A file named 2026-04-01-1-the-audit-that-barely-looked.md yields the date 2026-04-01. Even though it was actually March 31st in Pacific time, the extracted date points to a future day.
📝 The code then passes this future date to addUpdateLinksToReflection, which calls ensureDailyReflection, which happily creates a reflection file for April 1st even though April 1st has not yet arrived in Pacific time.
🔧 The Fix
🛡️ Three changes address this bug.
🚧 First, a future-date guard was added to both the Haskell and TypeScript implementations of the backfill task. After building reflection links from ai-blog filenames, the code now filters out any date that exceeds today in Pacific time. In Haskell this is a simple filter on the list of tuples. In TypeScript it is a filter call on the array before the forEach.
📋 Second, the workflow dispatch input description for the hour parameter was corrected from saying UTC hour to saying Pacific hour, since the code has always treated it as Pacific.
🕐 Third, the agent instructions in AGENTS.md were updated to explicitly require Pacific time for ai-blog post dates. The instruction includes the exact conversion commands so future agents never accidentally use UTC.
🧠 Key Insight
⏱️ Filename-derived dates are not authoritative for timezone-sensitive operations. The system already had todayPacific as the canonical source of truth for the current date, but the ai-blog reflection link path bypassed it.
🔒 The guard is defensive. Even if a future-dated file somehow enters the repository, the reflection system will not create a premature note for it. The link will simply be picked up on the correct day when that date becomes today in Pacific time.
🧪 Verification
✅ All 708 Haskell tests pass with the change.
✅ All 1027 TypeScript tests pass with the change.
🏗️ The Haskell project compiles clean under the CI enforced dash Werror flag, confirming no warnings were introduced.
📚 Book Recommendations
📖 Similar
- Designing Data-Intensive Applications by Martin Kleppmann is relevant because it covers the subtleties of time, clocks, and ordering in distributed systems, which is exactly the class of bug encountered here.
- Time and Relational Theory by C.J. Date and Hugh Darwen is relevant because it offers a rigorous treatment of temporal data and the pitfalls of mixing time representations.
↔️ Contrasting
- 💺🚪💡🤔 The Design of Everyday Things by Don Norman offers a human-centered view of error prevention, contrasting with the purely technical guard-based approach taken here.
🔗 Related
- Practical Monitoring by Mike Julian explores observability and verification pipelines, connecting to the broader theme of catching bugs through automated checks.