If you wish this endpoint to move deals between stages, then it will return a timestamp value when you update the dealstage property.
If you need to subscribe to deal stage changes in portals where your OAuth app is installed, you can use the Webhooks API and use the deal.propertyChange subscription type, specifying the dealstage property. The webhook notifications will include a occurredAt timestamp.
If you aim to retrieve historical timestamp values, however, you must export the history of the dealstage property in your portal. This can be done for all deals at once, as outlined in the Export property history section of this article.
If you wish this endpoint to move deals between stages, then it will return a timestamp value when you update the dealstage property.
If you need to subscribe to deal stage changes in portals where your OAuth app is installed, you can use the Webhooks API and use the deal.propertyChange subscription type, specifying the dealstage property. The webhook notifications will include a occurredAt timestamp.
If you aim to retrieve historical timestamp values, however, you must export the history of the dealstage property in your portal. This can be done for all deals at once, as outlined in the Export property history section of this article.