Let's begin with Laylat al-Qadr...
We all know the great virtue of Laylat al-Qadr (the Night of Decree), which most people probably consider to be the twenty-seventh of Ramadan. We find in authentic hadiths that even if it’s not the twenty-seventh, it definitely falls under the last ten nights of Ramadan (although there is some difference of opinion regarding this).
The rewards of any good deeds in Laylatul Qadr is multiplied an incredible number of times. As Allah (swt) says, it’s better than 1000 months: