The answer is immediately. If you already have your passport check the expiration date and confirm it does not expire within 6 months of travel because they won't take it. If you do not have a passport you need to find a post office near by that you can get one at. Passports use to take 6 weeks but with COVID they are taking anywhere from 3-6 months so don’t wait!
About 6 months before travel date. We suggest downloading an app called "Hopper". It allows you to track flights out of specific airports with dates and provides insight on best time to book your flight.
If you are only coming for a short period of time in the village, you do not need to rent a car. There will be a bus available on Thursday, July 14th headed to Monemvasia for a day trip. We will provide transportation on the evenings of Friday, July 15th and Saturday, July 16th. The taxis in the area are slow but manageable. If you do decide you would like a car, talk with your friends and family about splitting the costs of renting a vehicle together. We found a decent rate through rentalcars.com. You will need to have an international drivers permit that you can get from AAA. You will need to fill out an application and bring $20 as well as 2 passport pictures. Typically I waive the insurance offered but because it is an international rental my insurance company does not cover it so I opted in for the insurance.
You can take a cab or arrange other transportation from the airport to where you are staying in Athens. There is a bus that you can take to Gythion from Athens. Be mindful of where you stay in Mavrovouni/Gythion if you do not rent a car. You will probably want to stay where you are walking distance to the beach.
https://www.ktel-lakonias.gr/en/routes/item/1807-gythio-athens-athens-gythio