他們是同期的員工，所以很要好。 英文求翻譯?

They are buddies because they joined the company at the same time.
They joined the company at the same time and became good friends.

Having employed in the same period, then they became the colleagues as the result, very nice to one another. Yip

Because they was recruited into the company within the same recruiting period, they became good friends with each other after.