# in the fifth year and ninth month of Jehoiakim ... king of Judah

"after Jehoiakim ... had been king of Judah for more than four years, during the ninth month". The ninth month of the Hebrew calendar; during the last part of November and first part of December on Western calendars. 

# of Jehoiakim son of Josiah, king of Judah

See Jeremiah 25:1.

# proclaimed a fast

"told everyone that they were going to fast"