Merge pull request #207541 from baanders/8-10-data-history

ADT: Add sourceTime note

Author: PRMerger15

articles/digital-twins/how-to-manage-twin.md

@@ -5,7 +5,7 @@ titleSuffix: Azure Digital Twins
 description: See how to retrieve, update, and delete individual twins and relationships.
 author: baanders
 ms.author: baanders # Microsoft employees only
-ms.date: 02/23/2022
+ms.date: 08/10/2022
 ms.topic: how-to
 ms.service: digital-twins
 
@@ -230,18 +230,19 @@ The patch for this situation needs to update both the model and the twin's tempe
 
 ### Update a property's sourceTime
 
-You may optionally decide to use the `sourceTime` field on twin properties to record timestamps for when property updates are observed in the real world. Azure Digital Twins natively supports `sourceTime` in the metadata for each twin property. For more information about this field and other fields on digital twins, see [Digital twin JSON format](concepts-twins-graph.md#digital-twin-json-format).
+You may optionally decide to use the `sourceTime` field on twin properties to record timestamps for when property updates are observed in the real world. Azure Digital Twins natively supports `sourceTime` in the metadata for each twin property. The `sourceTime` value must comply to ISO 8601 date and time format. For more information about this field and other fields on digital twins, see [Digital twin JSON format](concepts-twins-graph.md#digital-twin-json-format).
 
 The minimum stable REST API version to support this field is the [2022-05-31](https://github.com/Azure/azure-rest-api-specs/tree/main/specification/digitaltwins/data-plane/Microsoft.DigitalTwins/stable/2022-05-31) version. To work with this field using the [Azure Digital Twins SDKs](concepts-apis-sdks.md), we recommend using the latest version of the SDK to make sure this field is included.
 
-The `sourceTime` value must comply to ISO 8601 date and time format.
-
 Here's an example of a JSON Patch document that updates both the value and the `sourceTime` field of a `Temperature` property:
 
 :::code language="json" source="~/digital-twins-docs-samples/models/patch-sourcetime.json":::
 
->[!TIP]
->To update the `sourceTime` field on a property that's part of a component, include the component at the start of the path. In the previous example, this would mean changing the path from `/$metadata/Temperature/sourceTime` to `myComponent/$metadata/Temperature/sourceTime`.
+To update the `sourceTime` field on a property that's part of a component, include the component at the start of the path. In the example above, this would mean changing the path value from `/$metadata/Temperature/sourceTime` to `myComponent/$metadata/Temperature/sourceTime`.
+
+>[!NOTE]
+> If you update both the `sourceTime` and value on a property, and then later update only the property's value, the `sourceTime` timestamp from the first update will remain.
+
 
 ### Handle conflicting update calls