How Stagging time is determined in STO ?

Hi SAP,

We have a issues with the Wrong Determination of Staging time in Purchase Order.

When we are creating a purchase document type in Production, staging and delivery date- time gets determined.

We also have a APO System in Connection.

As per them , the staging time is wrong. They believe it is getting determined from P01 system

My analysis is -

The STO is happening between 2 plants - Vendor being in Singapore and Receiver being in Australia.

When I click on Availability Check, I am re-directed to APO Screen which is APO System.

For Material Staging Date , we are following a Singapore calendar which is UTC+8 and when the delivery is confirmed for the receiving plant in Australia it is 2 hours ahead+ staging date which is because of the calendar settings on the plant level which is UTC+10.

But, I would like to understand how the staging date and more specifically time is determined in the first place. Is it coming from APO or getting determined in SAP SD under scheduling agreements.

Because , in my current issue- the discussion is more on time, then date

Please suggest as it is impacting one day while running services.

BR