DAY. The Muslim day commences at sun-set; our Thursday evening, for example being the beginning of the Muslim Friday. The Arabic Yaum denotes day in contradiction to the night (lail). The days of the week are as follows: –
Yaumu ‘l-ahad, first day. Sunday.
Yaumu ‘l-isnain, second day. Monday.
Yaumu ‘s-salsa, third day. Tuesday.
Yaumu ‘l-arba, fourth day, Wednesday.
Yaumu ‘l-khamis, Thursday.
Yaumu ‘-jam’ah, Day of Assembly, Friday.
Yaumu ‘s-sabt, Sabbath Day, Saturday.
Of the days of the week, Monday, Wednesday, Thursday, and Friday, are esteemed good and auspicious; the others evil (Qanun-I-Islam), p. 043). Friday is the special day appointed by Muhammad for meeting in the chief mosque for public worship. [FRIDAY.]
DAY OF JUDGEMENT. [RESURRECTION.]

Based on Hughes, Dictionary of Islam