In Virtualbox, when installing MS-DOS you can change the date in the machine. There are BIOS dates for the builds of Chicago or any beta builds of any OS that you need all over the place. Normally I install MS-DOS and set the date to the correct date for the specified build, then install Chicago and it works fine for some of the builds. VMware there is an actual BIOS you can go to which is very convenient. Some do upload VHD's out there just to save all the hassle for you to deal with. I did that in my Chicago Build 122 tutorial.
Discuss any edition of DOS, Windows 1.x, Windows 2.x, Windows 3.x, and Windows 9x