Petitions circulated pursuant to § 22.1-57.2 or 22.1-57.4 may be circulated for a period not to exceed one calendar year. If the period from the date of the earliest signature to the latest signature exceeds one calendar year, all signatures shall be invalid. At the time the petitions are filed, the petitions shall contain the required number of signatures of voters who are currently registered to vote in the county. Persons signing petitions for a referendum to be held at the November general election shall date their signatures on the petitions.