The Sharran attacks seemed to have at least started during Ilyn Toth's exile there. I think I remember him writing about conspicuous proceedings and unknown riders. That was during or maybe before the Year of the Unstrung Harp, 1371 DR. It depends on when Toth left Thay and when he arrived in Moonhaven. There's also a bit of a muddle regarding the timing of Melodia's and Isobel's deaths and Ketheric's subsequent "relapse" to Shar worship and thus new Dark Justiciars who would attack places of Selûnite worship. I remember some sources in Reithwin giving dates in the 1390s while WotC-sources seem to retcon the events to the 1370s which, however, clashes with established lore. The Shadow Curse was set upon the Reithwin area in or around the Year of the Wrathful Eye, 1391 DR according to in-game sources. Neither date works with Khelben fighting in the war and dying during the events of the Blackstaff novel which I think is set in the mid-1370s. Unless, the mentioned Khelben was his grandson, Khelben, the Younger, or unless the actual Khelben Arunsun, like Myrkul and Bhaal, wasn't really that dead after 5e purged a lot of 4e continuity.
