My 2 daughters were born at Phoenix Arizona, USA.
The birth times are Phoenix local times.
As from my studies, the time use in Ziwei is the "local time". No further adjustment is needed. The local time has already adjusted with different time zones. Different Time Zone come from rotation of earth against sun. That is why sun is always right above our head at 12:00 at everywhere in the world (on earth) because of Time Zone .
Except China, China does not has time zones. That is why people born at China need to know which area of China. China should have several Time Zones. USA has 5 Time Zones, from Hawaii to Maine(East Coast).

Please also comment on my wife's interaction with me and 2 daughters.