you can change the date and time in BIOS settings. unfortunately this could also mean a dead CMOS battery. since this is a Thinkpad of a few years, i suggest you replace the CMOS battery first. check the hardware maintenance manual for T20 for the location of the CMOS battery. http://www-307.ibm.com/pc/support/site.wss/MIGR-4UYM3F.html

to get into BIOS settings, try pressing F1 when IBM logo appears during boot.

as for the FAN error, it may mean that your fan is not working or not connected. either way you may need to open the laptop up to know for sure.

 

If your getting a Fan error on IBM laptops, you need to replace the CPU fan. It may still be working, but not at the speed of which it should.

You can look up this information by going to lenovo's website, click service and support, type in your model 4digits on the bottom of the laptop not the T20, click the manuals link and dowload the hardware maintence manual. Tells you every error code, beep code, and even dissassembly of the laptop sometimes.