Abstract: A long-lasting illuminated calendar designed for analog watches. A calendar date disk with see-through numbered indicia corresponding to sequential calendar days is mounted above a main plate which moves relative to the calendar disk at the rate of one date indicia per day. The illumination is provided by a sealed glass tube with a luminescent coating inside which is permanently activated, preferably by a limited quantity of tritium gas. The sealed glass tube is positioned in a recess formed in the watch plate. The light emitted from the gas tube projects through the transparent or translucent indicia in the calendar date disk.