The Question and Answer section for Little Women is a great resource to ask questions, find answers, and discuss the novel.
Marmee has a very special relationship with her daughters. She is the moral center of the family, she guides them with love, and she grooms her daughters to be good wives and mother's. Through Marmee, the girls learn that in any relationship, love...
From the text:
In her first effort at being very, very good, she decided to make her will, as Aunt March had done, so that if she did fall ill and die, her possessions might be justly and generously divided.
I don not think the time span of one year is explained in the text. Volume one of the novel, from the original text, ends with Chapter 23 and spans one year, from Christmas to the next Christmas. It could have to do with father being away.