def coherenstimestring(s):
   """
   Returns time string s in COHERENS model compatible format: YYYY/MM/DD;hh:mm:ss:fff
   """
   ns = s[0:4]   + "/" + s[5:7]   +"/" + s[8:10]  + ";" \
      + s[11:13] + ":" + s[14:16] +":" + s[17:19] + ":" + s[20:23]
   return ns