Our agent services customers in Australia with the format DD/MM/YYYY. When a user says "my birhtday is 3rd July 1998", it's correctly transcribed as 3/7/1998. However when the agent reads the model output to confrim the DOB with the called, it says "to confirm, your birthday is March 3rd 1998". Is there any way to fix this behavior? I've tried to set in prompt and don't think there is a setting. Sample call id: 019a20af-db56-7cc0-be58-753c0e505664

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To ensure your agent reads dates in the correct Australian format, add a formatPlan replacement to your voice configuration. This will force the TTS engine to say "3rd of July 1998" instead of "March 3rd 1998":

json
{
  "voice": {
    "formatPlan": {
      "enabled": true,
      "replacements": [
        {
          "type": "exact",
          "key": "3/7/1998",
          "value": "3rd of July 1998"
        }
      ]
    }
  }
}

Apply this in your assistant's voice settings to control how specific dates are spoken. For more details, see the documentation on formatPlan replacements. Source: - [Debugging documentation](https://docs.vapi.ai/debugging)

Vapi support bot's solution is a solution to a single date.

Hi bobbychick, Thanks for raising this and for sharing the sample call ID — I understand how critical it is to have dates read back in the correct Australian format. The root cause here is that when your LLM outputs

3/7/1998

, the TTS engine interprets it using U.S. date conventions (MM/DD/YYYY). To avoid this, the best solution is to have the LLM output dates in an unambiguous written format. Here’s the recommended adjustment: In your system prompt, add the following instruction:

When confirming dates with the user, always write them out in full format. 
For example:
- Write "3rd of July 1998" or "July 3rd, 1998" 
- Never use numeric date formats like "3/7/1998" in your responses
- This ensures dates are read correctly to Australian customers

This way, when the assistant confirms a birthday, it will say: "To confirm, your birthday is the 3rd of July, 1998" — which the TTS engine will read back properly. Let me know once you’ve tried this, and if you’d like, I can also suggest backup approaches (like formatPlan replacements) if numeric formats still come up. Best regards, Kyle

Thanks Kyle, we tried this and it worked. For future ref in case anyone else comes across this - This behavior differs between voice provider models. When using 11Labs multilingual models, it interprets as UK/Aus formatting while turbov2.5 reads in American TTS so seems that model is not just English, but locale is also US. - Possibly a recent change as we didn't have this issue a few months ago