Is delaying the Maghrib prayer until the light fades and darkness appears, and praying it a short time before the Isha prayer, considered unlawful (haram)? And is delaying the Isha prayer until after 3:00 AM considered unlawful (haram)? And are those who do so referred to as "neglectful" (sahoon)?

It is not permissible to offer the prayer outside its prescribed time, as Allah the Almighty says: "Indeed, prayer has been decreed upon the believers a time-bound ordinance." It is permissible to delay the Maghrib prayer until just before the entry of the 'Isha prayer's time, though it is preferable to perform it at the beginning of its time. Delaying the 'Isha prayer until after midnight is not recommended; some scholars consider its time to end at midnight, becoming a make-up prayer thereafter. Others consider it a time of necessity, with sin incurred for delaying it without an excuse, while the majority view the permissibility of performing it after midnight, though it is contrary to what is most preferable.