A period of time commonly used to evaluate financial results such as a company's performance or investment returns. Twelve months is a relatively short time frame, but it is a period long enough to generate a meaningful set of data.
Also called trailing twelve months (TTM). This term is often found in a company's financial statements.
A twelve-month period can provide a useful set of data for a number of reasons. For example, when evaluating the earnings of a retail company, data from one quarter would not provide an accurate picture of performance since retail companies do most of their business around the winter holidays. When evaluating an investment, a twelve-month period is sometimes long enough to smooth out the effects of short-term swings in the market, and give an idea of the investment's potential future direction.
Investment dictionary. Academic. 2012.