It takes 12 hours to receive and send mail in Guangzhou.

It takes 24 hours from Guangzhou to Kaifeng, Henan.

It takes 12 hours for the mail to reach you from Kaifeng.

The total time is 48 hours.

But the days are three days.

Because the post office delivers mail during the day, night, morning and afternoon. There are only two flights a day.

You can enter your email address and check it online to see if it is a timetable.