According to Rav Moshe Feinstein, ZT”L chatzot is always the same time ,11:56. Does this time change either forward or backward when the clock changes (winter or summer)? And is this time always the same in different countries?
Rav Moshe Feinstein (Iggros Moshe, Orach Chaim Vol. 2, no. 20) rules that halachic chatzos is at a fixed time throughout the year, which is the “solar noon” (when the sun crosses the meridian). This principle is also stated by the Aruch Ha-Shulchan (Orach Chaim 233:14).
This comes to 11:56 am in New York, and the time will be 12:56 for daylight saving time.
The time changes according to location, and in Jerusalem, for instance, it comes to 11:37am.