I've read the linked article. Complex. I'm just interested in updating the SPs for completed issues in an old sprint, whilst another sprint (2 sprints - 3/4 weeks later) is currently running. This is simply so we can update the Velocity report in JIRA in order to get an idea of the team's average velocity.
I'm still a little unclear as to the potential ramifications in doing this. Does it mess up the Velocity Report chart? Will I see two instances of the old sprint, e.g., in the chart? Similarly, will the Burndown chart update correctly?