Final answer:
Regular sessions of the United Nations General Assembly are held annually, while the U.S. Congress is mandated to meet at least once a year, commencing on January 3rd unless otherwise specified by law. State legislatures may meet less frequently, such as every two years in some cases.
Step-by-step explanation:
The question refers to the frequency of regular sessions of a legislative body. However, it's important to distinguish between different bodies as the details vary. When discussing the regular sessions of the General Assembly of the United Nations, they are held annually, typically starting in September. For the United States Congress, according to the Constitution and subsequent amendments, it is required to meet at least once every year, with the session commencing on January 3rd unless a different date is set by law.
For other legislative bodies, such as state legislatures, the frequency can be different. For example, in some states, regular sessions of the Legislature are held every two years in odd-numbered years and are not to exceed 140 days in duration. When special sessions are needed, they may be convened by the governor and typically cannot exceed 30 days.