DST time change

Hi experts,

We would like to understand how SAP derives times from the OS level. We always wanted to have Operating system's time as the SAP time. We have modified STZAC , STZBC transactions and removed the 'EST' time zone. We have also made sure that none of the user settings have EST time-zone.

Since we have our offices and branches only in the EST time zone, we would like to have the time taken only from OS level.

Any help would be appreciated.

Thanks

Peter