the third day of the month / three days

the tenth day of the month / ten days

two days, a two-day period / the second day after some set point in time / the second day of the month

all day

one day, 24 hours / the daytime, the period from dawn until dusk / (figuratively) a short period of time / one day, someday, an unspecified day / the first day of the month

a birthday

regular day off (e.g. closed every Monday)

the twentieth day of the month / twenty days / Short for 二十日鼠 (hatsuka nezumi): a house mouse

幾日も幾日も: day after day

(euphemistic) the world's oldest profession