This from the Guardian, as linked above:
"In his Australian traveller declaration, filed on 1 January, Djokovic declared “no” when asked: “Have you travelled or will you travel in the 14 days prior to your flight to Australia?”
The declaration is accompanied with a warning that giving false or misleading information is a “serious offence”, also punishable by civil penalties.
In documents filed to the federal circuit court, Djokovic said that on 1 January he authorised his agent to submit this declaration, before travelling to Melbourne from Spain via Dubai on 4 January.
In his interview with border force officials on 6 January, Djokovic confirmed the declaration was completed by his agent, “based on” his
Tennis Australia-approved medical exemption, but was not asked in the interview about travel in the fortnight before arrival.
A Twitter post by a Portuguese tennis reporter, Jose Morgado, appears to show Djokovic was in Belgrade at Christmas, posing with the handball star Petar Djordjic."
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The timeline doesn't work for the declaration that he made on his immigration papers.