When does the time for combining the Dhuhr and Asr prayers, and the Maghrib and Isha prayers, begin and end for a traveler, both as an advanced combination (Jam' Taqdeem) and a delayed combination (Jam' Ta'kheer)? And is it permissible to offer the Witr prayer after Maghrib if it is permissible to combine Isha with Maghrib?

If it is permissible for a traveler to combine prayers, then he may combine Dhuhr with Asr, either by performing them early (taqdiman) at the beginning of Dhuhr time (the sun's zenith), or by delaying them (ta'khiran) until the end of Asr time (before sunset). Similarly, for Maghrib and Isha, it is permissible to combine them either by performing them early (taqdiman) at the beginning of Maghrib time (sunset), or by delaying them (ta'khiran) until the end of Isha time (the appearance of true dawn). As for Witr after combining Maghrib and Isha early, it is permissible according to some scholars, but it is better to delay it until after the twilight (shafaq).