It's possible to get enough Vitamin D3 from sunlight alone, but it depends on various factors such as the time of day, season, latitude, skin color, and sunscreen use. In general, you need to expose your skin to sunlight for 15-30 minutes a day between 10 am and 2 pm without sunscreen to produce enough Vitamin. However, many people don't get enough sunlight exposure due to their lifestyle, location, or weather conditions.