Dexterity and Dates

If we look at the metadata fields at portal catalog we can see that there are a lot of date fields, some of them seem duplicates with different format, take a look:

Maybe i'm losing something, but this seems a mess for me, wouldn't be better to just keep a single format through all the dates and avoid having duplicates.
I guess the ones who have 'Date' on the name use the library DateTime, but anyways, i think that it would be better to just use one format, I see 3 different formats on the image.

I have to import some data to dexterity objects and I'm losing my mind trying to format to the correct date, and i don't know which field should i fill (created or CreationDate, ...)

that's already being addressed here:

Not exactly already addressed, but mostly discussed.

If anyone wants to take a lead on it I can help.

We should probably PLIP that though. Again I can help, but not lead unfortunately.