Does changing your site to https corrupts the piwik data?

I’m a newbie here, sorry if the question is a real newbie question …

My client would like to change his site from http to https, i.e. adding SSL to his site. Does he keep the old Piwik data or is Piwik considering this as a new site and will he lose the old data?

you can move on the fly but the site you want to track and the location of your piwik installtion have to be on a ssl site otherwhise you´ll get some small problems

Thanks!