Averaging Conventions
To avoid the complications of depreciating each asset from the specific date on which you placed it in service, the IRS and GAAP support guidelines that assume you place assets in service or dispose of them at designated dates throughout the year. These guidelines are called averaging conventions. By assuming an average placed-in-service date, the amount of total depreciation allowed for all assets approximates the total depreciation that would be calculated based on the actual days in service.
Under GAAP and IRS rules, different depreciation methods use specific averaging conventions. See depreciation methods to learn which averaging convention it uses.
There are five averaging conventions: