Hawaii Organic Act § 30

The senate shall be composed of twenty-five members, who shall be elected by the qualified voters of the respective senatorial districts for a term of four years beginning with their election and ending on the day of the second general election after their election: Provided, however, That (1) senators elected at the general election of 1956 shall continue to hold office until the expiration of the terms for which they were elected and shall be deemed to have been elected from the new senatorial district in which they resided at the time of their election; and (2) that at the first session of the legislature subsequent to the general election of 1958, the legislature shall so assign the senators to long or short terms, that as nearly as possible one half of them, including the holdover senators, shall hold office for two years and the remaining senators shall hold office for four years. In the event that the legislature fails to make the necessary assignments of short and long terms for senators as herein required, the Governor shall do so.