Meursault says that the days “ended up flowing into one another. They lost their names.” What does he mean?

In prison, Meursault becomes habituated to life in incarceration. He is soon able to learn how to sleep in prison as well and progresses to sleeping two thirds of the day. He then has less time to kill. Soon he becomes enveloped in his routine of passing time so his days end up flowing into one another.