[Backend TODO] Complete implementation in src/types/date+time.lisp

This backend file contains TODO comments for pending work:

**File:** `src/types/date+time.lisp`

**Items to complete:**
- Line 41: `TODO: Determine in what time zone we should compute this for legal`

**Priority:** Medium
**Component:** Backend (Common Lisp)

Start by reading src/types/date+time.lisp around line 41 and inspect the surrounding date/time code. Determine the legally appropriate time zone for the computation and complete that TODO; the issue is done when the pending implementation is resolved in that file.

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