### Answer No, you don't need a separate dateTime tool. Retell provides built-in system variables for current date and time that require no configuration. [(1) ]() You can use

{{current_time}}

for the current time in

America/Los_Angeles

, or

{{current_time_[timezone]}}

for a specific timezone (e.g.,

{{current_time_Australia/Sydney}}

) . To use it, add the variable directly in your prompt like this: [(2) ]()

#context 
current date: {{current_time_America/Los_Angeles}}

There's also

{{current_calendar}}

and

{{current_calendar_[timezone]}}

which provide a 14-day calendar view. [(1) ]()

​ To learn more, see the sources I considered: [[1] Dynamic Variables](https://docs.retellai.com/build/dynamic-variables) [[2] Discord message from @tirath. on 2025-10-30](https://discord.com/channels/1186424376300679209/1186462578310910112/1433536607599853698) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

### Answer You can add dynamic variables like

{{current_time}}

directly in your prompts. [(1) ]() Where to add them: - In your agent's prompt – Just type the variable directly into the prompt text, for example:

Hello {{user_name}}, I understand you're interested in {{product_name}}. How can I help you today?

- In your begin message – The opening greeting your agent uses - In tool configurations – Including custom function URLs, tool descriptions, and property descriptions - In call handling settings – Voicemail prompts, transfer call phone numbers, and warm transfer instructions For Conversation Flow agents: You can set default dynamic variables in your agent's settings under "Security and fallback settings" → "Default dynamic variables" [(2) ]() . These serve as fallback values when specific variables aren't included in the call request. [(1) ]() You can also configure

default_dynamic_variables

via the API when updating your conversation flow. [(3) ]() Testing: When using the "Test LLM" feature in the dashboard, you can preset dynamic variable values in the AI chat interface. [(2) ]()

​ To learn more, see the sources I considered: [[1] Dynamic Variables](https://docs.retellai.com/build/dynamic-variables) [[2] Discord message from @mrearthbound on 2025-04-09](https://discord.com/channels/1186424376300679209/1186462578310910112/1359404734137503865) [[3] Update Conversation Flow](https://docs.retellai.com/api-references/update-conversation-flow) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

### Answer --- For appointment booking, you'd integrate the

{{current_time}}

variable into your tool configurations — specifically in the custom function that calls your booking API. [(1) ]() Where to use it: - Tool descriptions – Include the current time context so the LLM knows what dates/times are available - Custom function URLs – If your booking endpoint needs a timestamp parameter - Property descriptions – When defining parameters for your booking function Example approach: In your custom function's description or prompt context, you could include:

The current date and time is {{current_time}}. Use this to help the customer book an appointment.

For Conversation Flow agents: You can add tools at the conversation flow level that handle booking. The

default_dynamic_variables

field lets you set fallback values that are available throughout the flow. [(2) ]()

json
"default_dynamic_variables": {
  "company_name": "Retell Inc",
  "support_hours": "9 AM - 5 PM"
}

Important tip from the community: If you're using a custom function for booking, make sure to enable "Speak After Execution" — otherwise your agent may stop responding after the tool call completes. [(3) ]()

​ To learn more, see the sources I considered: [[1] Dynamic Variables](https://docs.retellai.com/build/dynamic-variables) [[2] Update Conversation Flow](https://docs.retellai.com/api-references/update-conversation-flow) [[3] Tool calling - AI agent doesn't reply back. Stops interacting](https://community.retellai.com/t/tool-calling-ai-agent-doesnt-reply-back-stops-interacting/327) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.