store: Fix: UTC/CST timezone ambiguity in transaction freeze/thaw scheduling — utils/timezone.py

graph/fixes/fix-utccst-timezone-ambiguity-in-transaction-freezethaw-sche-4579c9.md

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+---
+id: 4579c929-165e-4e96-a0f2-3604febf1734
+type: fix
+title: "Fix: UTC/CST timezone ambiguity in transaction freeze/thaw scheduling — utils/timezone.py"
+tags: [major-domo, timezone, transaction-freeze, production-fix, discord-bot, python, fix]
+importance: 0.75
+confidence: 0.8
+created: "2026-02-22T22:41:31.654639+00:00"
+updated: "2026-02-22T22:41:31.654639+00:00"
+---
+
+# Fix: UTC/CST Timezone Ambiguity in Transaction Freeze/Thaw Scheduling
+
+## Project
+major-domo / discord-app-v2
+
+## Problem
+Production container (`major-domo-discord-app-1` on Akamai) had ambiguous timezone config — `/etc/localtime` pointed to `Etc/UTC` but `date` reported CST. The transaction freeze/thaw task used `datetime.now()` (naive, relying on OS timezone), causing scheduling to fire at unpredictable wall-clock times.
+
+Additionally, `utils/logging.py` used `datetime.now().isoformat() + "Z"` — appending "Z" to a naive datetime is misleading (Z means UTC but the datetime had no tzinfo).
+
+## Root Cause
+- `datetime.now()` with no timezone argument produces a naive datetime, inheriting the OS/container timezone implicitly
+- Container timezone config was inconsistent between `/etc/localtime` and the OS `date` command output
+- Never rely on OS timezone in containerized environments
+
+## Fix
+1. Created `utils/timezone.py` with centralized timezone helpers:
+   ```python
+   from zoneinfo import ZoneInfo
+   from datetime import datetime, UTC
+
+   CHICAGO_TZ = ZoneInfo("America/Chicago")
+
+   def now_utc() -> datetime:
+       return datetime.now(UTC)
+
+   def now_chicago() -> datetime:
+       return datetime.now(CHICAGO_TZ)
+
+   def to_chicago(dt: datetime) -> datetime:
+       return dt.astimezone(CHICAGO_TZ)
+
+   def to_discord_timestamp(dt: datetime) -> str:
+       # Returns Discord <t:unix:R> format
+       ...
+   ```
+
+2. Changed `tasks/transaction_freeze.py` line 300:
+   - Before: `datetime.now()`
+   - After: `now_chicago()`
+
+3. Fixed `utils/logging.py` JSON timestamp:
+   - Before: `datetime.now().isoformat() + "Z"` (misleading Z on naive datetime)
+   - After: `datetime.now(UTC).isoformat()` (proper `+00:00` UTC suffix)
+
+## Verification
+JSON logs show datetime with `-06:00` CST offset and timestamp with `+00:00` UTC. Confirmed working in production after deploy.
+
+## References
+- PR #45 into `next-release`, merged to `main`
+- Closes Gitea issue #43
+- Key file: `utils/timezone.py` (new), `tasks/transaction_freeze.py`, `utils/logging.py`