Answer:
The irony of these lines is that Jonas lied about the busy pleasant night he had had and his father did it too, unaware that what he was doing was very wrong.
Step-by-step explanation:
These lines from The Giver show us great irony.
The irony is that that day, Jonas discovered how his father killed an innocent twin baby. This was not pleasant for Jonas, however when he tells his parents he says something else and that is the irony.
In turn, his father also lies saying that he had a busy and pleasant day. The irony is also in those words, since there is nothing pleasant in killing a baby. The irony is that his father did not know what he was doing, as these people have had all feelings and emotions suppressed, and he believed he was doing his job.