So you have a bunch of old logs and you want to put it all together into AWStats to put the historical data in. Firstly you have to remove any existing AWStats monthly data files from the data directory as AWStats won't enter log information from the past.
Then you need to use a script like the one below to feed the logfiles back into AWStats and have it regenerate the monthly data files:
Obviously change out the example logfile path above for your own. This is the only way I know of how to import historical log data into AWstats.
Monday, April 23, 2012
Category: Awstats — SkyHi @ Monday, April 23, 2012