A favourite story. A merchant visited a sage and asked him how long it would take for him (the merchant) to attain enlightenment. The sage thought for an instant, and while he did so a butterfly alighted on his hand. He said “Do you see yonder mountain, massive and made entirely of granite? The time it would take for this butterfly to reduce the mountain to dust with its wings is the time it would take you to attain enlightenment.”
There are various computations in both Hindu and Buddhist traditions of exactly how long a kalpa is. 4.23 billion years is one. The Buddha did not give the exact length of the kalpa in terms of years. However, he gave several astounding analogies to help understand it. For instance, he asked his followers to magine a huge empty cube at the beginning of a kalpa, approximately 16 miles in each side. Once every 100 years, you insert a tiny mustard seed into the cube. The cube will be filled even before the kalpa ends. Alternatively – a variant on the butterfly story – imagine a gigantic rocky mountain at the beginning of kalpa, approximately 16 x 16 x 16 miles (dwarfing Mount Everest). You take a small piece of silk and wipe the mountain once every 100 years. According to the Buddha, the mountain will be completely depleted even before the kalpa ends. And once, when some monks wanted to know how many kalpas had elapsed so far, Buddha gave the following analogy. If you count the total number of sand particles at the depths of the Ganges river, from where it begins to where it ends at the sea, even that number will be less than the number of passed kalpas.
On a lighter note (below) the chocolate industry has not failed to see the potential inherent in these vast tranches of time. No doubt this chocolate bar lasts incalculably longer than its rivals.