I want to generate a statistic of number of publications by year from a set of bibliographic records (internal PICA+ format, but I could convert for instance to MARC2 or MODS). Surprisingly several publications have not a simple publication year but an additional "original date" or uncertain dates or range of years etc. Is there an overview of most common types of publication dates and how they are encoded in bibliographic records?
Take a look at ONIX code lists:
...especially List 163, Publishing date role and some of the other "date role" lists for an overview of what the publishing industry considers important to describe...