An 8 day weight driven clock will keep time for eight days. When you pull the weights up to the top, they will continue to slowly move down for eight days while keeping time until they’ve reached the end.
Weight driven clocks date back to the 13th century where they were first used in churches. Weight driven cuckoo clocks use weights to power its movement. On cuckoo clocks these are the heavy metal pine cones that you see hanging from the chains.