According to the
Croatian government, travelers entering the country must present a vaccine credential no older than 270 days, or just under nine months.
For
Austria, the vaccine certificate is valid for 270 days after the second dose for two-dose vaccines. The rules are slightly different for people inoculated with the Johnson & Johnson vaccine, which is valid after the 22nd day for 270 days. Under the rules, fully vaccinated travelers — even those eligible to enter other EU countries — would be treated as if they were unvaccinated
unless they also got tested upon arrival.