Added note about divergence from DateTime Scalar specification (#7407)

website/src/docs/hotchocolate/v14/defining-a-schema/scalars.md

@@ -184,12 +184,14 @@ scalar UUID @specifiedBy(url: "https://tools.ietf.org/html/rfc4122")
 
 A custom GraphQL scalar which represents an exact point in time. This point in time is specified by having an offset to UTC and does not use time zone.
 
-The DateTime scalar is based RFC3339.
+The DateTime scalar is based on [RFC 3339](https://datatracker.ietf.org/doc/html/rfc3339).
 
 ```sdl
 scalar DateTime @specifiedBy(url: "https://www.graphql-scalars.com/date-time/")
 ```
 
+> Note: The Hot Chocolate implementation diverges slightly from the DateTime Scalar specification, and allows fractional seconds of 0-7 digits, as opposed to exactly 3.
+
 <Video videoId="gO3bNKBmXZM" />
 
 # .NET Scalars