Today, I'm listing the auspicious days from Hesiod's Works and Days; the special days in a month where things should or should not be done. Note that the Hellenic calendar is lunar, so the month begins on the day after the first sliver of the moon is seen. You can read the full text of Works and Days is here.
As most of these don't relate to modern life or the life of a non-farmer, I don't practice all of them, but it's good to know this was something that at least a portion of the ancient Hellens thought. Perhaps there are some you can integrate into your own life? I know I pay special attention on the days where a God or Goddess is involved, and I take care to ask for a bit of extra protection on the unkindly days.
"Mark the days which come from Zeus, duly telling your slaves of them. [...] For these are days which come from Zeus the all-wise, when men discern aright."
- Hesiod 'Works and days'
4. Sacred, good day to bring home a bride, good day to begin building narrow ships; open a jar on this day
5. Unkindly day; sacred - Horcus (Oath), Eris (Strife)
7. Sacred - Leto, Apollon, Artemis
8. Good working day, good day to castrate boars and bulls
9. Good working day
10. Good for the birth of males
11. Good working day - Shearing sheep, reaping fruit
12. Good working day - Shearing sheep, reaping fruit, female works, castrating mules
13. Best day for setting plants, good day to set out supplies; worst day for the start of sowing
14. Sacred day, good for the birth of a female, good for taming sheep, shambling, horned oxen, guard dogs and mules
15. Unkindly day; sacred - Horcus (Oath), Eris (Strife)
16. Good for the birth of males (though he will be 'fond of sharp speech, lies, and cunning words, and stealthy converse'), good day for castrating sheep and children, good day for fencing in a sheep-cot; unfavorable for plants, bad for the birth of a female, bad day to get married
17. Sacred - Demeter, throw down grain on the (threshing) floor; good for cutting beams for houses and ships
19. Improves towards the evening, harmless to men in the month Hekatombaion; good day to get pregnant or to give birth to either boy or girl; never an unkindly day
20. Wise men should be born
24. Good day in the morning, less so towards evening
25. Unkindly day; sacred - Horcus (Oath), Eris (Strife)
27. Good day for opening wine-jars, good day for putting yokes on oxen, mules and horses, good day for bringing ships out of dry dock
"These days are a great blessing to men on earth; but the rest are changeable, luckless, and bring nothing. Everyone praises a different day but few know their nature. Sometimes a day is a stepmother, sometimes a mother. That man is happy and lucky in them who knows all these things and does his work without offending the deathless gods, who discerns the omens of birds and avoids transgressions."
- Hesiod 'Works and days'