Today is the 19th of January, 2013. Which means 19th of January, 2038 is now exactly 25 years away from us.
Why does it matter? Because at 03:14:07 UTC on 19th of January 2038 we will run into the Year 2038 Problem.
Many Unix-based system can't handle dates beyond that moment. For example, common Unix-based phones today won't let you set the date beyond 2038. This applied to all iPhones and Androids we tried it on (iOS is based on BSD and Android is Linux). Obviously this does not apply to Windows Phones, which let you set the date all the way to year 3000.
Yes, 25 years is a long time. But Unix-based systems will definitely still be in use at that time. And some things can start failing way before 2038. For example, if your Unix-based system calculates 25-year interests today, it better not be using time_t for the calculations.