Going on past experience, it's usually around the 12th of the month. Anything indexed after that time will not enter into the main index on the next dance.
However, google is always moving the goalposts, so I could be completely wrong
I was going to say 10th of the month myself, but I will be honest and say I really not sure If you can start promoting the site (with content) 2 months before your real live date but of course that is not always possible.
I launched a new site today, linked it to my best other pages which get visited by google every other day for updates. so fingers cross it will be added by everflux soon.
My last big launch, had my site receiving google traffic within 48 hrs can i beat this.
UPDATE New site already top of chosen keywords on Google.
I have done the same as you Purple, added links from a PR6 and PR7 site. which get indexed daily. Also submitted the url to google earlier on today.
However last time I 'launched' a site everflux picked it up and I received traffic a for a few days, then it stopped, also not included in the update. Hopefully it will be back this Month - fingers crossed.
If you can start promoting the site (with content) 2 months before your real live date but of course that is not always possible. 
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