Reminds me of a little calendar application I was told to update when I first started working at my current job. It was a portlet/JSP app meant to pull data on events (conferences, seminars, etc.) from a database it shared with another app that allowed users to create and register for events, and then show them on the appropriate dates on a little calendar. The event data was passed around the calendar app as an array of Strings, usually called data[].
data[0] was the title of the event, data[1] was the start date of the event (as a String with a two-digit year, e.g. "12/24/08"), data[2] was the end date (again, as a String), and data[3] indicated whether the event should show up on weekends on the calendar. It would be either null or the empty String (depending on where in the code it was constructed) for weekdays only, "*" for Saturdays, "**" for Sundays, and "***" for both Saturdays and Sundays. None of this was documented anywhere in comments, design documents, etc.