Night usually represents evil then why is Shivratri celebrated during night? The night after Maha Shivratri is ‘amavasya’ (full dark night). A day when the world will be completely dark. Symbolically, nothing but only ignorance and injustice will prevail. This ‘amavasya’ also represents ‘Kaliyuga.’ Mahadev Shiva appeared just before the beginning of Kaliyuga to rid the world of ignorance and evil. This was during the night before ‘amavasya.’
Therefore special worship is done before ‘amavasya’ to please Shiva who is the remover of darkness, evil and ignorance.
Then, almost all the legends associated with Shivratri happened during night and this is another reason.