And what is it that you can do to confuse your friends and family? Confuse 28 Days Later with 28 Days. In fact, to add insult to injury to this admittedly easy mistake, when someone discusses the 2002 horror movie say, with disgust, "Ew. Are you talking about the Sandra Bullock movie?" Gets them every time!
Here are details regarding these similarly tittled movies (and more!):
2000 drama starring Sandra Bullock. Bullock stars as a drunk forced to choose between jailtime or 28 days in rehab. She takes rehab, where she briefly takes up with a sex addict (Viggo Mortensen!), faces her addition, and befriends an abhorrent representation of a gay stereotype, unfortunately played by the otherwise awesome Alyn Tudek (I'll watch just about anything if he's in it).
The title refers to the amount of time in rehab.
28 Days Later
2002 horror/thriller film directed by Danny Bolye (Old People may remember him as the director of Slumdog Millionaire and Trainspotting) about a zombie-like pandemic. It's scary, and fun, but good too. And it's gory, bloody, and full of people getting bashed in the head with blunt objects, which is significantly different than rehab. The title refers to a passage of time as the protagonist wakes from a coma 28 days after the outbreak to face a bleak world.
28 Weeks Later
2006 sequel, sans Boyle. Now it's 28 weeks after the outbreak, and the world is a scary, scary place. It's good too! But still not about rehab or quirky Sandra Bullock.