The expert mode in Bimmercode can tweak things not supported in the 'normal'/default mode. I did use it in that mode on my GT after I located the specific codes required for the new battery. I have not tried that with the i3, but it may be possible.
Does anyone know the code names of the required fields?
Note, the Foxwell 510 scan tool has some capabilities in this area. Also note that Bimmercode app was updated in the last week or so, so check for updates. Don't know what they added. Sometimes, there's little tweaks that aren't listed in the description. On my GT, the scan tool was able to set the install time info, but had issues with the battery size change. I found the code and used the expert mode in Bimmercode to then change the size (I put a larger one in). Since you're not changing the size, all you need to be able to change/reset is the installation time, and the scan tool may work. ECSTuning sells the same thing as a Schwaben branded item, but you need to go to Foxwell's site to update the firmware.
2011 535i x-drive GT, 2014 i3 BEV