The events of the Book of Esther took place during the Persian period of ancient history (539-331 B.C.) and during the reign of King Ahasuerus in particular (486-464 B.C.).
The first historical event to which the writer alluded seems to be Ahasuerus' military planning session at which he plotted the strategy for his ill-fated campaign against Greece (1:3-21). The king held this planning session in the winter of 483-482 B.C. The last recorded event in Esther is the institution of the Feast of Purim that took place in 473 B.C. Therefore the events recorded in the book spanned a period of about 10 years.7
By the time Esther opens many Jews had returned from the Exile to Palestine to reestablish the institutions of Judaism (Ezra 1-6). Most of the Jews in exile did not return even though their law (Deut. 28) and the prophets (Isa. 48:20; Jer. 50:8; 51:6) encouraged them to do so. They preferred the comfort and convenience of life as they had come to know it outside the Promised Land to the discomfort and privation involved in obeying God. Esther and Mordecai were among those who chose not to return.8
The events of Esther fit chronologically between chapters 6 and 7 of Ezra.