Maybe you could make a clock based on a cylinder of sealed powder. You draw the time on it, and when it's time to update, you rotate the cylinder enough to mix the exposed powder and draw the next time.
Maybe the same thing could be done with beads and something similar to the marble machines to replenish a screen of beads, then dump it when the time is invalid.
Maybe the same thing could be done with beads and something similar to the marble machines to replenish a screen of beads, then dump it when the time is invalid.