Employment as we know it is changing. The kinds of jobs where one person works for one employer for years — with health insurance, sick days, paid vacation and a retirement fund — are getting harder to find. Throughout the economy, companies have pivoted to outsourced, subcontracted, freelance, temporary or gig workers. Many of those jobs don’t have benefits; some of them don’t even pay minimum wage. And while it’s accelerated during recent recessions, the trend has been decades in the making. This season, “The Uncertain Hour” is looking at this thing we used to call employment: what happened to it, why it happened and what a workforce made up of “nonemployees” means for our future. The new season starts Wednesday, Feb. 3. Here’s a preview.