What duration defines T-bills as short-term obligations of the U.S. government?

T-bills, or Treasury bills, are defined as short-term obligations of the U.S. government with durations that are less than one year. They are issued in a range of maturities: commonly 4 weeks, 8 weeks, 13 weeks, 26 weeks, and 52 weeks. The primary purpose of T-bills is to provide a way for investors to lend money to the government for a brief period, thus serving as a financing option for federal operations while also offering investors a relatively low-risk investment opportunity.

The characteristic of being less than one year is crucial for the classification of T-bills, as it differentiates them from other types of government securities like Treasury notes and Treasury bonds, which have longer maturities. This classification is significant in the context of financial markets, as different investment strategies may be employed based on the duration of the security.

While other options suggest various durations that either extend beyond one year or classify T-bills inappropriately within a certain range, they do not align with the established definition of T-bills. Thus, the clarification of T-bills as short-term instruments exclusively underlines the importance of understanding the term structure in the landscape of government securities.