Is 27 Rajab the night of the Prophet’s Night Journey and Ascension (al-Isra’ and al-Mi`raj)?

Is this Hadith sound?... It was narrated that the Prophet (peace be upon him) said: “Whoever says in Rajab ‘I ask Allah for forgiveness, there is no God but He alone, with no partner or associate, and I repent to Him’ one hundred times, and ends it with charity, Allah will decree for him mercy and forgiveness. And whoever says it four hundred times, Allah will decree for him the reward of one hundred martyrs.”

Are There Special Rewards for Fasting in Rajab?