Adjective
Lasting or continuing seven years; as, septennial parliaments.
Happening or returning once in every seven years; as, septennial elections in England.
Source: Webster's dictionaryAs the frequent elections were deemed inconvenient, the Septennial Act 1715 extended the maximum to seven years, but the Parliament Act 1911 reduced it to five. Source: Internet
In 1716, the Septennial Act was passed, which had a number of consequences. Source: Internet