Hello everyone . I'm having trouble with Vapi sending incorrect date/time format , even tho i specify that both in the tools and the prompt , yet everytime it send the data via api it always got it wrong . Can anyone help me with this issue ? https://cdn.discordapp.com/attachments/1437574839593599090/1437574840398909661/Screenshot_2025-11-10_171147___Vapi_preferred_date_error.png?ex=693fe7a6&is=693e9626&hm=366cb46c1fb8afa161aa563e95ed6ba84eafd43a949f5fb03eaef0f97eecab63& https://cdn.discordapp.com/attachments/1437574839593599090/1437574840923066469/Screenshot_2025-11-10_174348___preferred_date_error_2.png?ex=693fe7a6&is=693e9626&hm=dd2b88956159d9e54215ba2f570efdd464f4b998e16110cc30cc8f37536380df& https://cdn.discordapp.com/attachments/1437574839593599090/1437574841652744344/Screenshot_2025-11-10_174548_preferred_datte_error_3.png?ex=693fe7a7&is=693e9627&hm=060ff3f4d0222cfda10ae89de7cdb410b180af2fb4d81c13c26e026c5557862d&

Hey! I can help with this. The issue is likely that Vapi's AI is interpreting/formatting dates naturally in conversation, but you need it to send a specific format (like ISO 8601) in the actual API payload. Quick question: Are you using function calling/tools to capture the date, or is it pulling the date from the conversation transcript? And what format are you expecting vs. what are you getting?

So i'm expecting anything like : 2025-11-11T10:00:00 (November 11, 2025 at 10:00 AM) and what i'm actually getting is just literal string {preferred_time} , just the place holder text

The issue is that {preferred_time} is just a placeholder - Vapi isn't actually extracting the date from the conversation. Fix: Set up a proper function parameter in your tool to capture the date/time value, with clear formatting instructions (ISO 8601). I can help you configure this properly if you want feel free to message me and we can get it sorted quickly! 👍

Please insert this code snippet anywhere into your assistant prompt to provide correct date and times. Modify the timezone as needed:

The current date and time is {{"now" | date: "%A, %B %d, %Y, %I:%M %p", "America/Los_Angeles"}}

Do not use startTime and endTimes that are older than {{ "now" | date: "%s" | times: 1000 | tz: "America/Los_Angeles" }}

More information on this can be found on the documentation:

Thanks a lot Kyle