It seems the approach described in this old-ish post still works (slighly modified):
Searching for ‘Module’ in the RHP, then seeking backwards 70 bytes gives the first of the four releavant bytes. The first int16 is the date (since 1 Jan 2000), the second one is the time (only counting every other second).
This only seems to work for Python packages created with the RhinoScriptCompiler.