TZ env var ignored in Windows Bash — date returns UTC instead of local time

Problem

When running TZ=Asia/Tokyo date +%Y-%m-%d\ %H:%M:%S in Windows Bash (Git Bash / MSYS2), the TZ environment variable is silently ignored and UTC time is returned instead of the specified timezone.

Steps to Reproduce

On Windows with Git Bash:

TZ=Asia/Tokyo date +"%Y-%m-%d %H:%M:%S"
# Returns: 2026-04-19 13:39:49  ← UTC (wrong)

Get-Date -Format 'yyyy-MM-dd HH:mm:ss'
# Returns: 2026-04-19 22:40:28  ← JST (correct)

Expected Behavior

TZ=Asia/Tokyo date should return JST (UTC+9).

Actual Behavior

Returns UTC regardless of TZ setting. The offset is exactly 9 hours, confirming TZ is completely ignored.

Impact

Claude Code's global rules recommend using TZ=Asia/Tokyo date +%Y-%m-%d for JST-based timestamps. This guidance produces incorrect (UTC) results on Windows, causing 9-hour date/time errors in logs, filenames, and other time-sensitive operations.

Workaround

Use PowerShell instead:

powershell.exe -Command "Get-Date -Format 'yyyy-MM-dd HH:mm:ss'"

Environment

• OS: Windows 11 Pro
• Shell: Git Bash (MSYS2-based)
• Claude Code version: (latest)