星期 Xīngqí
Pronounced like “sheen-g chee”
Xīngqí means week

Naming the days of the week follows a 星期 + Number format all with the exception of Sunday.
Starting from one, 一, and ending at six, 六, the days of the week are as follows.

星期一 is Monday
星期二 is Tuesday
星期三 is Wednesday
星期四 is Thursday
星期五 is Friday
星期六 is Saturday

星期天 is Sunday

今天是星期六。
Jīntiān shì xīngqí liù.
Today is Saturday.

昨天是星期五。
Zuótiān shì xīngqí wǔ.
Yesterday was Friday.

明天是星期天。
Míngtiān shì xīngqí tiān.
Tomorrow is Sunday.

星期三我吃二十七饺子。
Xīngqí sān wǒ chī èrshíqī jiǎozi.
Wednesday I ate twenty-seven dumplings.