To understand how SAP calculates depreciation you'll want to see how they've approached the NewDCP with the introduction of time intervals.
Details on SAP’s New Depreciation Engine (Part 1): Introduction
This blog series introduces the NewDCP that SAP has rolled out in ECC.
S/4HANA Changes for Project Systems (PS)
What has SAP changes in S/4HANA for PS?
Depreciation Changes in 2017 Tax Cuts and Jobs Act
Read more on some of the upcoming depreciation changes from the 2017 Tax Cuts and Jobs Act.
What is a Cost Segregation Study and How Do I Do it in SAP?
Simply put... what is a cost segregation study and how is it handled in SAP?