By the ninth day of the fourth month

This is the fourth month of the Hebrew calendar. It is during the dry season. The ninth day is near the beginning of July on Western calendars. Zedekiah had been king for ten years, three months, and eight days. (See: rc://en/ta/man/jit/translate-hebrewmonths and rc://en/ta/man/jit/translate-ordinal)

city

This refers to Jerusalem.