Querying / Reporting on Install Date of Office Applications

Question

I am trying to create a query/report that looks for recently installed applications that require extra licensing costs from Microsoft, including Visio and Project.  I've made some really good reports for what applications are installed on what machines,
but where everything breaks down is the install date.  Since Office applications are patched monthly, the install date reported by our inventory changes each time the applications patch.  This gives me reports that seem to think that hundreds of
users have installed these applications in the last month.
The install date in both the Installed Software and Installed Applications classes shows the date of the last update installation, not the original installation.  
On sample machines, Programs and Features shows the correct original installation date, but I can't find where that date is coming from.  I have checked HKLM\Software\Microsoft\Windows\CurrentVersion\Uninstall, HKLM\Software\Wow6432Node\Microsoft\Windows\CurrentVersion\Uninstall,
and HKLM\Software\Classes\Installer\Products, and the install date shown is the date the application was last updated.
Any ideas on how to collect the correct install date by expanding my hardware inventory?  Or create a better query to use the data I have, possibly the History classes?

Answer 1

On a single test machine, I found a match, for the date displayed in "Installed Programs" vs. "Installed Updates"
This string/value seems to have the correct date (but it could be complete coincidence).
I theorised that the date against this specific Office Setup component, could be static (but who really knows. it's just a guess on my part.)
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{90150000-0116-0409-1000-0000000FF1CE} | InstallDate
Don
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