В третий месяц начали класть груды, и в седьмой месяц кончили.
They began doing this in the third month and finished in the seventh month.
In the third month they began to pile up the heaps, and finished them in the seventh month.
In the third month they began to make the heaps, and finished them by the seventh month.
They began piling them up in late spring, and the heaps continued to grow until early autumn.a
In the third month they began to lay the foundation of the heaps, and finished them in the seventh month.
In the third month they began laying them in heaps, and they finished in the seventh month.
In the third month they began to lay the heaps, and finished them in the seventh month.