三天。以下为确认函原文:
If you would like to reschedule or cancel your exam, you will need to provide the definite reschedule or cancel requirement to the NEEA / Prometric Regional Registration Center no later than 16:00 THREE full days prior to your scheduled test appointment (not including the day of your test or the day of your request). There will be a ¥400 RMB ($ 50 USD) fee for rescheduling your appointment, Reschedule can not be made without both reschedule definite requirement and reschedule fee before the deadline(报名中心在收到具体更改要求和更改费后方能按要求为考生更改).