Greece is temporarily extending quarantine for those entering the country

As of 08.01.2021 to 00:01 on 21.01.2021, those arriving in Greece by air, land or sea are subject to a seven-day 
quarantine, instead of the three-day quarantine applied so far.
There remains a requirement for a negative PCR test, performed up to 72 hours before entering the country, 
for a completed PLF form, with a generated QR code, 24 hours before the trip, as well as for mandatory testing 
with a rapid (antigenic) test at border crossings. If the rapid test is positive, the person will be 
quarantined for 14 days.
Upon entering the country, travelers must have filled in a residence address (in PLF format), 
where they will spend the specified quarantine. It is possible to leave the country earlier, 
before the quarantine expires. 
The fine for non-compliance with the quarantine is in the amount of 5,000 (five thousand) euros.

Restrictions on crossing the border remain, and in the period from 23:00 to 07:00 this is prohibited.