title: python time subtraction
body: <p>I want to get the time in Python.  With <code>time.ctime()</code>, there are lots of functions: </p>
  
  <p>I tried:</p>
  
  <pre><code>def write_time():  
    NUMBER_OF_MIN=40 #my offset
    obj=time.gmtime()
    print  " D", obj.tm_mday, " M",obj.tm_mon,  "Y",obj.tm_year, 
    " time", obj.tm_hour+TIME_OFFSET,":",   obj.tm_min-NUMBER_OF_MIN, ":",obj.tm_sec
  </code></pre>
  
  <p>I want to subtract 40 minutes from the time. </p>