Hi Russell,
I know this thread is about 4 years old, but could you please confirm that there's still no way to add historical markers via python in 10.3?
Thanks,
Stephan
There is still no way to create a historical marker via python as of 10.3.1. However you can connect to your geodatabase at a point in time using python. If you use the Create Database Connection tool (which was new at 10.1 I believe). This tool lets you specify a point in time you wish to connect to. This will connect to your archived data at that point in time. Not quite a historical version but pretty close.