Sometimes it becomes big deal to do little things. Same applies for me to change batteries. I have an alarm clock, and needed a battery change. So many times I forgot to get some batteries from store, and once I Had it, forgot where did I put. But finally day came, when I can do it. I got my clock, opened the place to install the batteries with screw driver. The slot was kind of rusted, but worked. Then with help of pointy side of screw driver, I clicked the old batteries out. The one I had them before took them out, now I looked for negative and positive , both on batteries and on place where I had to install them. Because if you do not install them right , it is not going to work right.  I put them in, then adjusted the time on clock, and reset the time for alarm, 
Question: How long did it take?
a few minutes