一般现在时代替过去时

一般现在时代替过去时的例句解释：

1 )"书上说"，"报纸上说"等。

The newspaper says that it's going to be cold tomorrow.

报纸上说明天会很冷的。

2) 叙述往事，使其生动。

Napoleon's army now advances and the great battle begins.