29 CFR §452.104

1. (a)The statutory requirement for giving fifteen days' notice of election is a minimum standard. There is no objection to giving more notice than is required by law. However, it was clearly the intent of Congress to have members notified at a time which reasonably precedes the date of the election. For example, notice in a union publication which is expected to cover elections to be held six months later would not be considered reasonable.
2. (b)Should a union change the date of an election from the date originally announced in the mail notice to the members, it must mail a second notice, containing the corrected date, at least fifteen days before the election.