The phrase "numbered day" refers to the idea that each day of our lives is limited and counted. It reminds us that time is passing, and we should make the most of every day because we only have a certain number of days in our lives. Full definition
When hired, they are immediately placed into the trenches where they crunch numbers all day long, isolated over long periods of time. (blog.simplyhired.com)
The problem was solved by taking my vitamin on even numbered days. (attachmentparenting.org)
Guided Practice 54 - added instructions to number the days of the week. (excelmath.com)