When is prepatch?

[Vanillataur-nethergarde-keep]

Blue post says it:

@Kaivax

We haven’t locked down the specific timeframe for when this buff will activate, but we expect it to last for at least 6-8 weeks; beginning a few weeks before the 3.4.0 Pre-Patch and persisting right up until the day that Wrath of the Lich King Classic launches.