You can't change the date if your return has already been accepted, but according to the IRS website at Pay Taxes by Electronic Funds Withdrawal,

• Once your return is accepted, information pertaining to your payment, such as account information, payment date, or amount, cannot be changed. If changes are needed, the only option is to cancel the payment and choose another payment method.
• Call IRS e-file Payment Services 24/7 at 1-888-353-4537 to inquire about or cancel your payment, but please wait 7 to 10 days after your return was accepted before calling.
• Cancellation requests must be received no later than 11:59 p.m. ET two business days prior to the scheduled payment date.