Actually they are talking about the same thing, only with different focuses.
老人活动室里,大家有的闭目养神,有的谈论古今。
In the old people's activity room, some are refreshing their spirit with closed eyes while others are talking about things that happened in both ancient and modern times.
骋怀纵酒,谈古论今。
Enjoy yourself to the your heart's content, indulge yourself with wine and talk over the past and the present.
我最喜欢和朋友们把酒临风,谈古论今。
I like talking most about things of ancient times and present with friends, raising our wine glasses against wind.
赶紧收起你的那些奇谈怪论,我们并不想听。
Don't talk about your ridiculous arguments, we don't want to hear them.