Waht are the different shitos regarding chazot hoyom or night?
Answer:
Please see the recent article published on the subject here: https://dinonline.org/2012/01/26/parshas-bo-the-halachic-time-of-chatzos/.
The main shitos are either:
1) The same as chatzos of the day (midway between haneitz hachamah and shkiya).
2) A fixed time for the entire year (same as chatzos of the day, but fixed time based on the solar noon).
3) Midway between Tzeis Hakochavim and Alos Hashachar.
Please see the above article for more details.
