After the filing of a nomination petition by or on behalf of a proposed candidate for a city office, such candidate shall not be permitted to withdraw unless a written notice of withdrawal is served on the city clerk no later than 4:00 o’clock, local time, in the afternoon of the third business day after the last day for filing petitions as in this charter provided, unless the third business day falls on Saturday, Sunday or city holiday, in which case the notice of withdrawal may be served on the clerk up to 4:00 o’clock, local time, in the afternoon on the next regular business day.