I have a bunch of old watches in my jewelry box that have been there for years. I decided to see if I could fix one up as my usual watch quit working. It was a digital watch which would no longer tell time, although some numbers would come up. So I trashed it. I found an old nice looking Seiko watch and decided to try and change the battery. After many failed attempts to get the back cover off, I went to You Tube to see if there was an instructional video that would help. So I did a search for "How to replace a watch battery" and found a few videos. In one video the woman used a very sharp knife to pry the back off. Bingo !! I had a razor knife and tried that and yep it worked, where everything else I tried failed. So I was able to get the battery out and went to the local pharmacy and they had the right battery number. So then I bought it and brought it home and put it into the watch. Then I lined up the back watch cover with the watch stem, and snapped it back on. Watching the You Tube video helped me to do this right.
 
So now my old Seiko watch is working again after years of sitting in the jewelry box. Yea !!
I just saved myself about $50-100 bucks for a new watch !!

Youtube is my go to source for all sorts of things from new music by totally unknown bands and artists to learning how to skin a deer in under 2 minutes, to building all sorts of things that would never be allowed through airport security....and more.
 
Another way to get the battery changed...... take the device to Batteries Plus. They will open it, pop in a new battery and the only cost is the battery. I personally have not worn a watch in 3 decades. I don't need to know the time that urgently. When I do there are clocks all around me.... in the car, the truck, the house, the phone.....
 
And in the words of that great Chicago tunesmith..... Does anybody really know what time it is? Does anybody really care?

 +1 to what Guitarhacker said. My MIL had given us three watches that didn't work to  see if we could fix them. I had the small tools and was prepared to try it but Batteries Plus did it for free, only the cost of the battery was involved.
 
 It is pretty amazing what is on youtube. In a few cases I went there thinking I had maybe a 1 in 100 chance of finding a video that pertained to what I needed, sure enough the info was there.
 
 

I think Wal*Mart does it too....I tried replacing batteries in a few more of the old watches without success, if fact I ended up trashing a couple of them. I've got one more to do, but I'm going to take it to Wal*Mart to do, as I can't get this one open myself. And I don't want to trash it.
 
I was able to get a second watch working so I'm happy about that. But I learned that it's very easy to trash a watch.

I saved my pennies and bought a watch free from batteries this year. I feel liberated.

Oops, sorry.  Thought I was going to get to watch somebody replace a battery.

I took my last watch to Wal*Mart and the girl there replaced the battery in about 5 minutes. I was really struggling with this one and couldn't get it opened. She had all the right tools right there to do the job....so now I have three running watches !!