File dir = new File("/sdcard/Files/");
File[] files = dir.listFiles();
for (int i = 0; i < files.length; ++i){
long lastTime = files[i].lastModified();
Date nowDate = new Date();
long nowTime = nowDate.getTime();
if (nowTime - lastTime > 60*60*1000){
files[i].delete();
}
}
Надеюсь, это поможет вам.