By starting the Tanaka's SLink (Devil) on 1/31 you can skip finishing Tartarus and fighting Nyx entirely while still getting the true ending.

Devil SLink requires raising Hermit SLink to rank 4, having at least rank 4 courage, and 40000 yen. After getting rank 4 Hermit, Tanaka will be at Paulownia Mall every day of the week until you start his social link. Normally on 1/31 you cannot do any activity at Paulownia Mall that would consume time, however you can still talk to Tanaka. By timing the third time you give him money to be on 1/31 you can start his social link and skip the rest of the night, bypassing being forced into Tartarus. The game will skip right to 3/03 and you will still get the true ending.

This does NOT work with the Tower social link. He doesn't appear in the club on 1/31.

I tested and this does NOT work in Portable. Tanaka only shows up in Paulownia mall on Tuesdays and Saturdays even before starting his social link.
Supposedly Tanaka in P3 Vanilla is a daytime social link making this not possible in Vanilla either. I haven't tested this for myself though.

In a Hard, True End speedrun this is estimated to save ~7-8 hours making sub 16h pretty free.

All credit for finding this goes out to some random gamefaqs poster: https://gamefaqs.gamespot.com/boards/...

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