A strange clock

I don't turn away quartz clocks needing new movements but they are of no particular interest. This one struck me as rather strange as I could not figure out why it has a calendar on it. It tells me there are 7 days in the week, 12 months in the year and 31 days in some months but it is no help in determining the actual day and date! No coffee out or walk today as I am in work all day covering absence.