Which school of magic is Mordenkainen most closely associated with?

Which school of magic is Mordenkainen most closely associated with? In particular, I’m not interested in speculation or opinions, but rather if such a thing has ever been outright stated in any officially released D&D material, or which can at least be objectively inferred from things like the sorts of spells he was most closely associated with.

He has made an appearance in a couple of 5e adventures:

Speaking of the spells he has created, in 5e there are four spells that include his name in the title:

  • Mordenkainen’s faithful hound (4th level conjuration spell)
  • Mordenkainen’s private sanctum (4th level abjuration spell)
  • Mordenkainen’s sword (7th level evocation spell)
  • Mordenkainen’s magnificent mansion (7th level conjuration spell)

The above might imply that conjuration is his “main” school of magic because he made a whole two of those, but I know that there is also a 9th level abjuration spell called Mordenkainen’s disjunction from 3.5e, which puts abjuration and conjuration on an even keel (or possible even that abjuration is the “winner” because that’s the highest level spell he made), so I’m not sure if this method of inference gives a clear answer after all (since I’m not limiting this to simply what is in 5e).

So, has there ever been any clear mention in any official material regarding which school of magic Mordenkainen is most closely associated with, or can it be inferred from official material if not?

How old is Mordenkainen in the Curse of Strahd adventure?

According to most wiki pages surrounding the character, Mordenkainen was born in 509 CY. The last entry that used the Greyhawk calendar year was when mentioning how he started to shave his head in 591 CY. With this information in mind, if most adventures in the Forgotten Realms take place during 1491 DR, then how old would Mordenkainen technically be during the Curse of Strahd adventure?

Also, how would you go about converting the present DR to Greyhawk’s CY?

My sources for information:

  • Mordenkainen’s entry on the Greyhawk: Return to the Classic wiki on Obsidian Portal
  • The reddit post “5E Official Adventure Timeline” by /u/AuraofMana on /r/DndBehindTheScreen