Answer: As mentioned above, there are only three kinds of days defined in Scripture. A day that needs to be discussed however is the 30th day of the month, which is called in astronomical terms, translation day. It occurs approximately every other month as counted from New Moon day. This day cannot be either a seventh-day Sabbath or a New Moon, but appears to be in the work day category, but perhaps for personal projects rather than employment. It is always the day following the fourth Sabbath of the month when the month is 30 days long, and it is then followed by New Moon day, otherwise on 29 day months; New Moon day follows the fourth Sabbath of the month. New Moon day and translation day are not counted as part of any week.
The importance of the translation day, lies in keeping the 12 month years totaling 354 days, and the thirteen month years totaling 385. This day is invaluable in bringing into harmony the Creator’s luni-solar year with the solar year every 19 solar years. This kind of adjustment is somewhat similar to the extra day in leap years of the Gregorian calendar.