[lowside]

Closes #967

Passes the gateway's configured timezone to ControllerApplication.new() so zigpy's ZCL Time cluster server can report the correct UTC offset and DST attributes (dst_start, dst_end, dst_shift) to Zigbee devices. Without this, zigpy reported a zero UTC offset and no DST, causing devices to display UTC rather than local time.

---

Changes

zha/application/helpers.py

• ZHAData.local_timezone default changed from datetime.UTC to None. None means "no timezone configured" and is passed through to zigpy as-is, correctly suppressing Master_for_Zone_and_DST claims for a timezone the user never set. The previous datetime.UTC default was only ever used by the Sinopé climate entity — it was never forwarded to zigpy — so there is no change in existing behavior.

zha/application/gateway.py

• local_timezone=self.config.local_timezone added to the ControllerApplication.new() call in _async_initialize, so zigpy's Time cluster receives the correct timezone at startup.
• Gateway.update_local_timezone(tz) added as the canonical way to update the timezone at runtime. Direct writes to gateway.config.local_timezone only update the ZHAData copy; this method keeps ControllerApplication.local_timezone in sync as well. If called before initialization or after shutdown, ZHAData is still updated and the controller will receive the correct value on the next async_initialize.

zha/application/platforms/climate/__init__.py

• SinopeTechnologiesThermostat._async_update_time now falls back to datetime.UTC when local_timezone is None, preserving existing behavior for unconfigured setups. datetime.now(None) returns a naive system-local datetime and would silently produce wrong secs_since_2k values on non-UTC hosts.

tests/test_gateway.py

• test_configured_timezone_passed_to_controller — parametrized over None and a real ZoneInfo; verifies both that the kwarg is forwarded to ControllerApplication.new() and that it lands on the controller instance.
• test_update_local_timezone_syncs_controller — verifies both ZHAData and application_controller are updated together, including clearing back to None.
• test_update_local_timezone_before_init — verifies no crash when called before async_initialize or after shutdown, and that ZHAData is still updated.

tests/test_climate.py

• Explicit assertion that local_timezone is None before the UTC fallback case, making the precondition clear.
• Updated to use gateway.update_local_timezone() for the runtime timezone change, consistent with the documented API.

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Notes

A companion change is recommended in homeassistant-core: the EVENT_CORE_CONFIG_UPDATE handler currently writes zha_gateway.config.local_timezone = ZoneInfo(hass.config.time_zone) directly, which bypasses ControllerApplication.local_timezone. Swapping that to zha_gateway.update_local_timezone(ZoneInfo(hass.config.time_zone)) will keep both copies in sync on runtime timezone changes without requiring a ZHA restart.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.23%. Comparing base (6decce1) to head (dad4e57).
⚠️ Report is 4 commits behind head on dev.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev     #974   +/-   ##
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  Coverage   97.23%   97.23%           
=======================================
  Files          61       61           
  Lines       10704    10710    +6     
=======================================
+ Hits        10408    10414    +6     
  Misses        296      296           

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[zigpy-review-bot]

Looks good. The change is small and does what the description says: local_timezone now reaches ControllerApplication.new(), which zigpy 2.4.0 (the pinned version) accepts as a keyword-only argument and stores on the controller, where the Time cluster reads it.

Verified (6 checks)

• The local_timezone kwarg on ControllerApplication.new exists in the pinned zigpy==2.4.0. The Time cluster reads application.local_timezone in _handle_read_attributes, and None means no zone authority (Master_for_Zone_and_DST is not set).
• The only runtime consumer of ZHAData.local_timezone in zha is the Sinopé _async_update_time. The None to UTC fallback keeps its behaviour identical to the old dt.UTC default, and datetime.now(None) would indeed have returned a naive local time.
• Home Assistant core already passes a ZoneInfo when it builds ZHAData (homeassistant/components/zha/helpers.py), so HA setups get the zone at startup with this change. The runtime EVENT_CORE_CONFIG_UPDATE path in __init__.py still writes config.local_timezone directly, which is the companion core change the description already calls out.
• update_local_timezone is safe before init and after shutdown, since application_controller is None in both cases.
• tests/test_gateway.py and tests/test_climate.py pass (118 passed). ruff check, ruff format --check and mypy zha/ are clean in the worktree venv, and CI is green on all three Python versions.
• The earlier docstring thread from puddly is resolved and the docstring is now a single line.

One optional nit is inline.

[Copilot]

🟡 Changes recommended

A timezone update during asynchronous controller creation can leave the controller reporting the previous timezone.

1 open issue

• Reapply timezone after suspended controller creation · New

What changed in this PR

This PR forwards ZHA’s configured timezone to zigpy so its Time cluster can report local offsets and daylight-saving attributes, addressing #967.

Changes:

• Pass the configured timezone at controller creation and add a runtime update method.
• Represent an unconfigured timezone as None, preserving the Sinopé thermostat’s UTC fallback.
• Add timezone forwarding and lifecycle tests, and update climate tests.

File	Description
zha/​application/​platforms/​climate/​__init__.py	Preserve UTC fallback when no timezone is configured.
zha/​application/​helpers.py	Default the optional timezone to None.
zha/​application/​gateway.py	Forward timezone configuration and support runtime updates.
tests/​test_gateway.py	Test timezone forwarding, synchronization, and lifecycle handling.
tests/​test_climate.py	Verify the fallback and use the runtime update method.

_{Review effort: Balanced}