As long as you can count one to seven, you can say Monday to Sunday easily in Chinese.

一yī , first tone, means one
二èr, fourth tone, means two
三sān, first tone, means three
四sì , fourth tone, means four
五wǔ , third tone, means five
六liù, fourth tone, means six
七qī , first tone, means seven

Add the word '星期 (xīng qī) ' in front of each number, you will get the days of the week.
星期 (xīng qī), first tone and first tone, means week or weeks
星(xīng), means star or stars
期 (qī), means terms

星期一 (xīng qī yī ) Monday
星期 二(xīng qī èr) Tuesday
星期 三(xīng qī sān) Wednesday
星期 四(xīng qī sì) Thursday
星期 五(xīng qī wǔ) Friday
星期 六(xīng qī liù) Saturday
星期 七(xīng qī qī) Sunday.

Note that 星期天(xīng qī tiān) 星期日(xīng qī rì) actually are more commonly used for Sunday.