stored in a dark place at about 20 degrees Celsius (68 degrees Fahrenheit) is one year after production for futsū-shu and honjōzō-shu, 10 months for ginjō-shu, junmai-shu, and sake pasteurized only once, and up to eight months for special namazake that can be distributed at room temperature. According to Sawanotsuru, once pasteurized sake and unpasteurized namazake have a best before date of nine months after production. Some sources also state that the best before date for unpasteurized namazake is three to six months after production. Namazake generally requires refrigeration at all times. However, there are exceptions to these storage conditions, in which case the conditions are stated on the label. For example, sake under the brand name Aramasa (新政) must be kept refrigerated at all times, even if it is junmai-shu, which has been pasteurized. Once the sake is opened, it should be kept refrigerated, as the flavor deteriorates more quickly than before opening. Best before date after opening the bottle varies depending on the source. According to sake media outlet Sake no shizuku, which interviewed several major sake production companies, the responses from all companies were nearly identical. According to the responses, junmai type sake without added distilled alcohol has a best before date of 10 days after opening, while other types of sake with added distilled alcohol has a best before date of one month after opening. According to the international sommelier of sake certified by SSI International, ginjō type sake, which is fermented at low temperature for a long time, has little flavor degradation for two to three days after opening and has a best before date of one week after opening. Other special designation sake and futsū-shu have little flavor degradation for 10 to 14 days after opening the bottle and have a best before date of one month after opening. Unpasteurized namazake deteriorates the fastest and should be drunk as soon as possible. These best before dates are shortened when stored at high temperatures or in bright places, especially under sunlight or fluorescent lights that emit ultraviolet rays. On the other hand, the optimal temperature to minimize flavor degradation is minus 5 degrees Celsius (23 degrees Fahrenheit). It is also recommended that sake bottles be stored vertically. This is because if the bottle is placed horizontally, the sake is exposed to more air inside the bottle, which speeds up oxidation and may change the flavor