update dynamic variables

Author: chdeskur

fern/assistants/dynamic-variables.mdx

@@ -6,7 +6,6 @@ subtitle: >-
 slug: assistants/dynamic-variables
 ---
 
-
 Prompts, messages, and other assistant properties can be dynamically set when starting a call based on templates.
 These templates are defined using double curly braces `{{variableName}}`.
 This is useful when you want to customize the assistant for a specific call.
@@ -67,3 +66,13 @@ meaning that you don't need to set them manually in `variableValues`:
 | `{{year}}`  | Current year (UTC)          | 2024                 |
 
 **Note:** You will need to add the `{{variableName}}` in this format in all your prompts, whether it is the first message or anywhere else you want to use it.
+
+## Advanced Date and Time Usage
+
+We use [LiquidJS](https://liquidjs.com/) for dynamic variables. You can use the `date` filter to format the date and time in the timezone you want.
+
+```liquid
+{{"now" | date: "%b %d, %Y, %I:%M %p", "America/New_York"}}
+```
+
+This should return the current date and time in New York.