Because its gonna get to Denver tonight/tomorrow anyways. If I cost myself an extra day whatever, if I get it first thing in the morning then I win. Pretty sure UPS can handle it.
Last minute changes with UPS never gets your package to you sooner. When you show up at the service desk and they don't have it (and they won't), there is no way for them to go back and find it. You won't get it until the next day.