adding advanced date and time usage in assistant dynamic variables

Author: sagar0581

assistants/dynamic-variables.mdx

@@ -64,3 +64,13 @@ 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.