Lesson Learned #051: Calendar Awareness is Critical for Trading AI

Date: December 19, 2025 Severity: HIGH Category: Operational Reliability

The Problem

Claude repeatedly made statements like “tomorrow could be down” without recognizing that:

  1. It was Friday evening
  2. Tomorrow (Saturday) is NOT a trading day
  3. The next trading day is Monday

This eroded user trust because:

  • The AI appeared unaware of basic market calendar
  • Users expect a trading AI to know market hours
  • Repeated mistakes made advice seem unreliable

Root Cause

The trading context hook did NOT prominently display:

  • The current day of week
  • Whether it’s a weekend
  • The actual date

The AI had to infer this from context clues rather than having it explicitly stated.

The Fix

  1. Added explicit calendar awareness to the hook: 
    DAY_OF_WEEK=$(TZ=America/New_York date +%A)      # Monday, Tuesday, etc.
FULL_DATE=$(TZ=America/New_York date '+%A, %B %d, %Y')  # Friday, December 19, 2025
IS_WEEKEND="false"
if [[ $DAY_NUM -ge 6 ]]; then
 IS_WEEKEND="true"
fi
  2. Made it the FIRST LINE of output: 
    📅 TODAY: Friday, December 19, 2025 ⚠️ WEEKEND - NO TRADING
  3. Clear weekend warnings so AI never forgets

Prevention

  • Always show current date/time prominently in trading context
  • Include day of week (not just date)
  • Warn explicitly on weekends
  • Reference “next trading day” not “tomorrow”
  • LL-012: Weekend Market Awareness
  • LL-013: Trading System Dead for 2 Days

Tags

#calendar #operations #trust #user-experience