Birch Retail, a fictional operations team, is combining small utilities into a local reporting workflow. The practice revisits calendar arithmetic, explicit locale formatting, virtual files, modules, chunked text, and the local assertion runner. Each task has a separate contract, so use its expected result shape rather than carrying an assumption from the previous exercise. Dates use explicit UTC rules or the requested time zone. File data stays inside the supplied virtual workspace, and chunks may split a label between two arrivals. The examples use fresh dates, labels, and test values. Keep an empty file separate from a missing file and a blank line separate from an unfinished buffer.