title: Dates in the xaxis for a matplotlib plot with imshow
body: <p>So I am new to programming with matplotlib. I have created a color plot using imshow() and an array. At first the axis were just the row and column number of my array. I used extent = (xmin,xmax,ymin,ymax) to get the x-axis in unix time and altitude, respectively.</p>
  
  <p>I want to change the x-axis from unix time (982376726,982377321) to UT(02:25:26, 02:35:21). I have created a list of the time range in HH:MM:SS. I am not sure how to replace my current x-axis with these new numbers, without changing the color plot (or making it disappear).</p>
  
  <p>I was looking at datetime.time but I got confused with it.</p>
  
  <p>Any help would be greatly appreciated!</p>