I have recently merged code to refactor Home Assistant to use only UTC times internally. A much needed refactor. I’ve added some extra test coverage to time sensitive parts to ensure stability. The code has been live in the dev branch for the last 9 days and will be soon released to the master branch.
From now on all internal communication will be done in UTC: time changed events, datetime attributes of states, etc. To get the current time in UTC you can call
homeassistant.util.dt.utcnow(). This is a timezone aware UTC datetime object.
homeassistant.util.dt is a new util package with date helpers.
There is also such a thing as local time. Local time is based on the time zone that you have setup in your
configuration.yaml. Local times should only be used for user facing information: logs, frontend and automation settings in
Setting up a time zone happens in
configuration.yaml. If you have no time zone setup, it will be auto detected using the existing detection code using freegeoip.net. You can find a list of compatible time zones on Wikipedia.
homeassistant: time_zone: America/Los_Angeles
The changes to the code are mostly backwards compatible. The old
hass.track_point_in_time use now internally two new methods:
hass.track_point_in_utc_time. The usage of the old methods have not changed and should be backwards compatible.
This refactor adds a new migration for the database adding a
utc_offset column to events and states. This information is currently not used but can prove useful in the future when we start analyzing the historical data.
All built-in components have been upgraded. The following list is only for people that run custom components:
hass.track_point_in_timewill now return a time zone aware datetime object. Python does not allow comparing a naive with an aware datetime object.
- the sun attributes for rising and setting are now in UTC. The methods
sun.next_setting(hass)are backwards compatible, just be careful if you used to read the raw attributes.
- the API sends all times in UTC. If you use anything else besides the frontend to talk to HA, make sure it handles it differently.