All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad, sallallaahu 'alyhi wa sallam, is His slave and Messenger.
Some narrations specify some particular days for cutting nails but all these narrations are not proved authentic as stated by Imam Ibn Hajar in his book Al-Fath.
What is confirmed in this concern is that no more than forty days are to pass without one clipping his nails. Also, one should clean them every Friday in order to be in a state of complete purity.
The rule in this regard is to clip them whenever there is a need as stated by An-Nawawi .
Allah knows best.