Date formats are messy
The "Date" column has variety formats, such as "2013", "Dec 17", "2022 Mar 21", or even month like "July" only. I don't know when the papers were published now. Does anyone know how to resolve this issue? Thank you.
Fully parsed dates will be normalized to a uniform format in a future version.
But this isn't something we can answer in the abstract. If you have some specific examples where you didn't get full metadata, provide URLs or DOIs (depending on whether you saved from the web or via Add Item by Identifier) and the Date value you got and we can say more.
Look towards the right side of the date field on the right pane. Does it not say "y m" in grey?
If not, maybe your translators need updating? There were some misreadings of Pubmed dates, but that was a long time ago. Make sure that automatic updating of translators are checked under Zotero Preferences -> Advanced.
(Also, why not save straight from Pubmed page within your web browser using Zotero's connectors? Much faster and easier to do than downloading citation files and importing.)