booleanmodified=file.setLastModified(now);// on some devices (e.g. Nexus 5) doesn't work
if(!modified){
modify(file);
if(file.lastModified()<now){
// NOTE: apparently this is a known issue (see: http://stackoverflow.com/questions/6633748/file-lastmodified-is-never-what-was-set-with-file-setlastmodified)
LogU.d("Last modified date {} is not set for file {}");