Worked on the reporting backend:

• With David and Stew's help, got the SQL query building worked out. We were hampered by the fact that we're on mySQL 4.0, so we don't have embedded SELECT available, and bracketing is a little unusual; ended up writing lots of pre-queries which are executed before the main query.
• Got the query working correctly, with the exception of trapping for when no selections are made; that should probably be prevented in JavaScript.
• Got the basic table output built.
• Added a permalink to a URL which will consist only of the report. Only the shell of this is done; the reports.php page can tell when it's a standalone, and it will supply header and footer eventually.
• Wrote the arithmetic stuff for figuring out minutes worked for all retrieved posts.
• Confirmed that the hooked-in CSS file is working (CSS is not written yet).