The days are getting longer, and better yet, Milwaukee is getting a sneak peek at spring this week. The sun will set about 5:24 p.m. in Milwaukee on Feb. 16, according to timeanddate.com. And the year ...

For generations, people have lived by the steady rhythm of a 24-hour day. It feels fixed and unchanging, something we rarely question. But scientists have long known that this cycle is not permanent.