Ask HN: Paid to go to a conference, but forced to take a day off what to do?

A friend works for an rather successful Italian startup.<p>As a developer, he'll be sent to a good conference this year. They'll pay him hotel and flight ticket. So far so good. But... They force him to take that day off, (holiday!)<p>I wonder how is it with USA/UK startups? If you're paid to go to a conference, will you have to get holiday for that day? What will you do if that happens to you ?