Night. The period comprised between dusk and dawn. In olden days night was a synonym of danger, thanks both to the natural fear that ponies have of the dark, and the very real threats that used to lurk within it.
But with the passage of time, as it is with all things, such fears eventually faded away. Progress and understanding dissipated the imaginary horrors that lurked in the darkness. And as ponies mastered the use of light, first with the magic of the unicorns and then with the invention of electricity, the shadows themselves were defeated.
But although the fear itself may have faded away, the reason of why it existed in the first place is still very real…