Marks certain days of the month (as the tenth, twentieth or thirtieth of every month); used when refering to any special anniversay day of s.o. who has died (as the 3rd, 7th, 10th, 20th, 40th, 70th, or 100th day).
I might go to Kota Kinabalu on the twentieth day of the month Muharam.
Tomorrow night is the seventh day after Father's death.