A timely application for an initial part 70 permit for an existing part 70 source is one that is submitted within 12 months after the source becomes subject to the permit program, or on or before such earlier date as the Division may establish. The earliest that the Division may require an initial application from such an existing part 70 source is 6 months after the Division notifies the source in writing of its duty to apply for an initial part 70 permit.