title: localtime not thread safe, but okay to call in only one thread?
body: <p>Am integrating another users code into mine.  They have library that calls localtime function which is not thread safe.</p>
  
  <p>I have noticed some strange problems.   If their code is restricted to one thread only can localtime still cause a problem?  Note in other threads of my code I call localtime_r ( the thread safe version ).</p>
  
  <p>Thanks.</p>