1the day after tomorrow
2acquired (not innate or congenital)
3a posteriori
4life after birth (the period in which one develops through experiences, contrasted with 先天)
Examples
zuó tiān昨天shì是xīng qī星期wǔ五，hòu tiān后天shì是xīng qī星期yī一。
昨天是星期五，后天是星期一。
Yesterday was Friday; the day after tomorrow is Monday.
你后天有时间吗？
Do you have time the day after tomorrow?
请后天来吧。
Please come the day after tomorrow.