What can cause the date of submission status to change without a change of status "under review" for Elsevier editorial systems?

When a paper is assigned to a reviewer, the reviewer may decline or fail to review the paper. In this case the editor will assign the paper to a new reviewer. The status date will change at the day the new review was assigned, but the status will remain the same.

There could me multiple reasions for the status date to change:

• Reviewer comments are added to the database
• The reviewer changes
• Editor checks the database

See this question: http://www.editage.com/insights/why-does-the-status-date-of-a-submission-change-periodically-though-the-status-remains-unchanged

For that you need to know how the journal system works. When status is "with editor" it doesn't always implies that the paper is not send for reviews. Because in journals the configuration of online submission system is such that if at least 2 or 3 reviewers have accepted the review request only then status will change to "under review". Also when status is "under review" and status date is changing then it means the reviewers have submitted his/her report in the system (which have led to change in status date). When at least 2 or 3 reviewers reports (this count is configured by the journal) are not come till then status won't change. If they come then status may change to "with editor" or "under editor evaluation" or "required reviews completed". Under these status also the status date may change which implies remaining reviewer(s) have also submitted their reports.