Originally Posted by llashero
It is 126.96.36.199
Would've thought that option would be on most OSs? Very odd.
The latest is 188.8.131.52, the link to it is stickied on the top of the page (PS - did you typo 184.108.40.206?). Although the OS shows as being for another carrier (TMO), you can load other carrier's OS's on your phone safely and successfully.
That said, perhaps another 8100 user running 220.127.116.11 or .101 can confirm first if they have the option to set the number of keep days before you go to the trouble of upgrading only to find it didn't add the functionality for you.
I keep dwelling on the "new 8100 owner" part of your initial post and am hesitant to outright recommend an upgrade, knowing how scary it might be to some.
Let's see if anyone using a more recent OS can confirm or deny the calendar keep days setting. I am running an 8800, handheld v18.104.22.168 which of course isn't the same phone; but the features are purportedly similar, to my understanding.