You may be considered a Greek tax resident if you are present in Greece for more than 183 days cumulatively during any 12-month period. Tax residency under this test applies from the first day of your presence in Greece. This day-count test does not apply if you are in Greece exclusively for tourism, medical, therapeutic, or similar private reasons and your stay does not exceed 365 days, including short periods abroad. Greece also has other tax-residency criteria, including permanent or principal residence, habitual abode, and center of vital interests.
https://aade.gr/en/greeks-abroad-non-residents/income-taxation/tax-residence-natural-persons-itc