Summary

Using the Get sprint endpoint to get Sprint data via REST API does not include the "true start date".

That is to the date the Sprint was actually started and not the value provided in the Start date which can be any date.

Proposed solution

An additional field needs to be added in the API to include the true start date:

{
"id": 34,
"self": "https://host.atlassian.net/rest/agile/1.0/sprint/34",
"state": "active",
"name": "New Sprint JSON 11",
"startDate": "2020-06-05T13:50:16.751Z",
"trueStartDate": "2020-06-08T13:50:16.751Z",
"endDate": "2022-09-09T14:33:00.000Z",
"originBoardId": 3,
"goal": ""
}