Job Executes Early When Cron Updated

If there is a job whose Cron schedule changes, and the schedule defines some point in time between the last scheduled run time and now, the job will run immediately.

For example, if I have a job set to run monthly on the 10th day, and on the 12th (after it has run), I change the Cron schedule to be monthly on the 11th day, the job will trigger to run immediately.

There should probably be a way of controlling this behavior on update.

Start by tracing where a recurring job's Cron schedule is updated and how its next run is computed; the issue names no files or tests. Done requires a maintainer decision about the update behavior or control mechanism, followed by coverage for changing a schedule across a missed run time.

Written by the indexing model from the issue text.