Middlemarch by George Eliot

Dorthea is noting Celia's observation and knowledge that exactly six months have passed.

“Dorothea, dear, if you don’t mind—if you are not very busy—suppose we looked at mamma’s jewels to-day, and divided them? It is exactly six months to-day since uncle gave them to you, and you have not looked at them yet.”

Celia’s face had the shadow of a pouting expression in it, the full presence of the pout being kept back by an habitual awe of Dorothea and principle; two associated facts which might show a mysterious electricity if you touched them incautiously. To her relief, Dorothea’s eyes were full of laughter as she looked up.

“What a wonderful little almanac you are, Celia! Is it six calendar or six lunar months?”

“It is the last day of September now, and it was the first of April when uncle gave them to you. You know, he said that he had forgotten them till then. I believe you have never thought of them since you locked them up in the cabinet here.”