How do I restore an original macbook air (2008) without a battery?

I bought this old macbook air a couple of days ago. It doesn't have a battery and It was running OS X 10.7 Lion. I wanted to restore it to 10.5 to speed it up. I restarted the mac in recovery mode using the recovery disk but reinstall OS X didn't work. I tried it again using usb recovery disk and it failed again. I later figured out that the reason it wasn't working was because the date was reset to 2001. Previously I simply couldn't boot to the usb because of this, but now I could. When installing OS X it said something like "Couldn't download the necessary components for installing OS X" although I was running the recovery from the usb disk. Some forums suggested partitioning the main disk completely and reformatting it. I did it and it cost me the recovery drive on the hard disk. But now I realize that I can't reset the date to 2016, so the mac doesn't boot from USB. And I don't have the recovery disk on the hard disk to fix the date. Since Macbook Air 2008 doesn't support internet recovery the only two options I see are:

1- Find a 8M/PATA to USB converter and install an OS X on the hard disk from another macbook.

2- Find someone willing to let me open their macbook air, replace their harddisk with mine and install an OS X.

Can you suggest me a 3rd (preferably easier) option?