The times of this book were some 400 years before the coming of Christ. It is set, I believe, in the days of Nehemiah. It speaks of a time when the second temple had been built, 1:10, 3:10. The sins with which it deals coincide with what we see dealt with in the book of Nehemiah. Malachi was likely occupying a similar position in Nehemiah's day as did Zechariah and Haggai in the day of Zerubbabel and Joshua. Malachi likely aided Nehemiah's reformation upon which he embarked when he returned from the Persian court to Jerusalem again and found that the people had relapsed into their former sins, Nehemiah 13:6-7. As a book to study in these days, it is particularly suitable and that for the following reasons: