What day of the week does Lina get off?

In the City of Ember, children receive jobs at age twelve. They graduate from school, and on Assignment Day they receive the jobs randomly by pulling job titles out of bags. They have to keep the job assignment for three years before requesting a new position. However, they are able to trade jobs, and Lina and Doon switch positions so Lina can be a messenger and Doon can work in Pipeworks.
Lina has every Thursday off of work. All workers between the ages of twelve and fifteen have a break on the same day of the week, Thursday. We learn this in chapter five, when Lina spends her day off shopping at Garn Square market and later walking to Night Street in search of colored pencils with Poppy. Lina works the other days of the week, so their neighbor Mrs. Murdo looks out for Poppy and Granny, whose mind is slowly deteriorating.