category: 天 (tiān): day, sky
今 + 天 (jīn tiān) = today
明天 (míng tiān) = tomorrow
昨天 (zuó tiān) = yesterday
后天 (hòu tiān) = the day after tomorrow
前天 (qián tiān) = the day before yesterday
五天前 (wǔ tiān qián) = five days ago
五天后 (wǔ tiān hòu) = five days after
