Gemini LLM (2.0 Flash) handles full day events from a calendar wrong, uses the wrong day.

[saschaabraham]

The problem

I have a calendar for my daughter, imported via the google calendar integration. The calendar is exposed to the LLM.
There is one full day event tomorrow (Sunday) 'e-Learning' defined for her.
If I ask today (Saturday), "Tell me the appointments from Nele on Monday.", the anser is "Monday Nele has a full day event 'e-Learning'".
Asking for appointments on sunday returns the 'e-learning' event too.
So, the full day event is reported to happen on sunday and monday, not sunday only.

Appointments on other days, no full day events, are reported correct.

This happens with the openai LLM, Default Settings too, so there is maybe an error in the used tool?

What version of Home Assistant Core has the issue?

2025.2.1

What was the last working version of Home Assistant Core?

No response

What type of installation are you running?

Home Assistant OS

Integration causing the issue

Google Generative AI

Link to integration documentation on our website

No response

Diagnostics information

No response

Example YAML snippet

Anything in the logs that might be useful for us?

Additional information

No response

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[tronikos]

This happens with the openai LLM, Default Settings too, so there is maybe an error in the used tool?

@balloob can you take a look?

[nathan-curtis]

I think it's timezones.

Calendars are saved in GMT.

You are in local time X

Suspect AI is reading GMT and misinterpreting.

Try this.

Add something to your prompt that tells the LLM something to the effects of. Your current local time is, (full timecode including timezone)
When reading calendars they are stored GMT unless told otherwise... you should convert time ones for the user humans can't timezone very well.

It seems to be working for mine - she 'Friday' messes up now and again now but for the most part she does time on calendars correctly.

Now to validate this is it and how to fix it permanently?