Where exactly does A Certain Scientific Accelerator fit in the timeline? Where exactly does A Certain Scientific Accelerator take place in the timeline? I know it'd some time after Accelerator's gunshot wound by the necklace but that's about it.
If you are wondering about the episode order:

The broadcasted Accelerator S1 arc happens after Index S1, episode 17 and Railgun S, episode 24. 

Which means the Accelerator S1 happens before Index S1, episode 18 and Index S2, episode 1, and Index S1 episodes 19-24, and Index S2, episodes 2-5.

Index S2, episodes 2-5, happens before A Certain Magical and Scientific Ensemble, which happens before the Index S2, episodes 6-7, which happens before the Index Miracle of Endymion movie, which happens before Index S2 episodes 8-24, and Index S3.