Correlation between products based on purchases placed around the same date
Association rule mining is nearly always done with the apriori or eclat algorithms. There are a few papers which have utilized these in the time series context. This paper details a thorough implementation, though this is done with relation to identifying gene patterns, rather than customer purchases. The idea is still the same though, only there is slightly less complexity in your case. Unfortunately, this does not give a detailed Python implementation.

Depending on your situation (this is unlikely to be applicable from your description, but I list this just in case...), it may be useful to break from association rules and cluster your data instead, provided you have enough of it to treat it as continuous. A Python implementation of this is featured in this article.

Good luck!