Answers.com defines Inception as
The beginning of something, such as an undertaking; a commencement.
For search engines inception date is the date on which a particular document of a particular link to a particular site was found during their regular crawling routine.
So does inception date really matters.
Yes we would say especially newly indexed sites its important we have a good inception date since it affects the overall ranking of a site by a huge margin. Since now all sites need to have a good trust with search engines its good if the inception into search results in much earlier so that trust is gained over a period of time.
Also backlink inception is very important since sudden growth or drop in backlinks gives an alarm signal to search engines. A steady growth in backlinks indicates good signs for a site.
Google’s patent says
“Consider the example of a document with an inception date of yesterday that is referenced by 10 back links. This document may be scored higher by search engine 125 than a document with an inception date of 10 years ago that is referenced by 100 back links because the rate of link growth for the former is relatively higher than the latter. While a spiky rate of growth in the number of back links may be a factor used by search engine 125 to score documents, it may also signal an attempt to spam search engine 125. Accordingly, in this situation, search engine 125 may actually lower the score of a document(s) to reduce the effect of spamming.”

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