alt Hacker NewsMy favorite retirement gift is a seven segment clock that points to the day of the week. It usually gets a laugh, followed up months later with an honest thank you and an anecdote about how it saved them from going to the bank on a Sunday or the like.
These are particularly interesting because they isolate the one part of time that is completely made up: the week. Days, months, years have natural markers - but weeks and particularly days of the week are a totally arbitrary coordination function.