add example time_of_day formats (#1768)

Author: kenjenkins

content/docs/internals/ppl.mdx

@@ -455,6 +455,16 @@ allow:
         before: 4:30PM
 ```
 
+Values for `after` and `before` should match one of these formats:
+
+- "3:04 PM"
+- "3:04PM"
+- "3 PM"
+- "3PM"
+- "15:04:05.999999999"
+- "15:04:05"
+- "15:04"
+
 ## Rego
 
 :::caution Rego Usage Requires Extreme Care