dow – Cal­cu­late day of week from a nu­meric date

De­fines two macros: — \dow­comp, which cal­cu­lates the day of the week as a num­ber in the range 0—6, re­turn­ing the re­sult in a counter \dow, and — \day­name, which uses \dow­comp to pro­duce the (English) name of the week day.