偕日出

1

所以每年的这个事件都被称作“偕日出”。

And this annual event is called a heliacal rising .
2

偕日出能够很好地告诉我们尼罗河将在何时被淹没。

The heliacal rising was a fair indicator of when the Nile would flood .
3

“偕日出”之后，一年最后一个月里的新月，标志着古埃及人新年的到来。

The next new moon , after the heliacal rising of Sirius , which happened in the last month of the calendar year , marked the New Year .
4

因为古埃及人的历法包括了月相和天狼星的“偕日出”，有的年份有12个月；如果天狼星没有在第12个月升起的话，那么当年就会有13个月。

And because the ancient Egyptians were using the lunar cycle in combination with this heliacal rising , some years ended up having 12 lunar months , while others had 13 lunar months , if Sirius didn 't rise in the 12th month .