from wikipedia:
"In
Castlevania: Grimoire of Souls, the Grimoires do not directly "see" the future, but rather act as magical, living archives that record all past, present, and future events of Dracula's history. They contain documented memories of every fight against Dracula, allowing characters to enter these records and experience or alter historical events."
So this means that Dracula is alive at the times of the GMD games, which while I'm not a fan of this theory could imply that the 3 LoS games are actually placed in the same universe as the other Castlevania games and not as 2 separate with just both Dracula's powers being linked by Chaos.
With this info I'd still put Harmony after the first GMD game, so the player can understand the reference, even tho it takes place prolly earlier when the Grimoire was created.
@Elly