I'tikaf

Aslaam u alaikum I wanted to ask that this year I plan to do itikaf as much as possible.  I won’t be able to do the whole time because I have small children and other household responsibilities,  but I will do in the night as much as possible.  Does  the next fasting day start after we break our fast at Maghrib time?  Meaning, will the 27th night the night of Laylatul Qadr start after we break our 26th fast, at Maghrib time.  Does the time for ibadaat for the night start after Maghrib or Isha, or someone told me it start after Asr,  especilally to find the time of Laylat ul Qadr.