Bulk Processed Files - dealing with duplicate periods across years

[klo9klo9kloi]

When looking at e.g. EIA930_2019_Jan_Jun_co2.csv, the period starts a few hours after 2019-01-01 00:00:00 rather than at the mark, which I'm guessing has something to do with UTC shifting.

Keeping that example file, if I then look at EIA930_2018_Jul_Dec_co2.csv, the period also overflows into year 2019 for a few hours, such that if I concatenate these two files then there are some duplicate periods.

If I am aggregating emissions by year, what is the proper way to deal with these duplicate period rows? Aggregate? Take the one from the latest year?