I have been trying to use the information provided at Christopher L. Bennett -- Star Trek DTI Alien Calendar Notes and create a date conversion in MS Excel between the Gregorian calendar and the various provided on the page.
I believe that the best way is to use the Julian day and thanks to Julian day - Wikipedia, the free encyclopedia I got the Gregorian to Julian to Gregorian down.

But I have been unable to adapt the Julian to Gregorian conversion to be Julian to Alien - and I am not even talking about reverse.

Hopefully someone can help me - or in the best case do the work for me so I can get my hands on the necessary equations.
If I am in the wrong place, please direct me to the correct one.

Thank you.

PS. I have no connection with the owner, it is just for my personal use.