Quote Originally Posted by Antonio1986 View Post
But how I will indicate that the feeling of boredom is not current but it was at the past. I was bored speaking at that day.
Is it: "Когда нам надоело беседовать, мы пошли купаться"
Since there is no subject (technically, the infinitive "беседовать" is the subject, not a noun), you need neuter, as for impersonal structures.

Antonio, there are two issues.

First, you are confusing two things: boredom and tiredness. It happens that English and Russian have different views on the human emotions spectrum. For Russians, they are just different emotions. You may be tired of something but not bored. You may feel boredom without any reason, without being tired of anything specific. You may be both tired and bored, of course, as one of the possibilities. What you are talikng about is tiredness, not boredom.

Second, the whole phrase "Когда нам надоело беседовать, мы пошли купаться" is already in the past. "надоело" is the past tense, "пошли" is the past tense as well.