Why does arXiv have a multi-day lag between submission and publication? If you go on the recent pages (now, 8th December 2020, 19:24 Italian time), there is for example the article &quot;Exploring the Usage of Online Food Delivery Data for Intra-Urban Job and Housing Mobility Detection and Characterization&quot;.
This article is under the heading &quot;8 December&quot;.
But if you click on it, it was &quot;Submitted on 4 Dec 2020&quot;.
Why there is a lag between submission time and the header under which it appears for recent publications?
I guess the arXiv staff have to approve the article before is being published .... is my guessing correct?
I guess the arXiv staff have to approve the article before is being published .... is my guessing correct?

Yes, arXiv moderates all submissions before posting them (there is some description of this here). This is not anywhere near as rigorous as peer review; rather, someone just flips through it to ensure that the submission is (1) not complete junk and (2) classified correctly. This approach is used by many pre-print platforms (SSRN, socarXiv, etc.).