The "zǐyuè" () is the period starting with Dàxuě (), i.e. the solar term "before" the winter solstice. The "chǒuyuè" () starts with Xiǎohán (), the term before Dàhán (), while the "yínyuè" () starts with Lìchūn (), the term before Yǔshuǐ (), etc. Thus in the solar system a month starts anywhere from about 15 days before to 15 days after its lunar counterpart. The branch names are not usual month names; the main use of the branches for months is astrological. However, the names are sometimes used to indicate historically which (lunar) month was the first month of the year in ancient times. For example, since the Han dynasty, the first month has been "jiànyínyuè", but earlier the first month was "jiànzǐyuè" (during the Zhou dynasty) or "jiànchǒuyuè" (traditionally during the Shang dynasty) as well. For astrological purposes stems are also necessary, and the months are named using the sexagenary cycle following a five-year cycle starting in a "jiǎ" (; 1st) or "jǐ" (; 6th) year. The first month of the "jiǎ" or "jǐ" year is a "bǐng-yín" (; 3rd) month, the next one is a "dīng-mǎo" (; 4th) month, etc., and the last month of the year is a "dīng-chǒu" (, 14th) month. The next year will start with a "wù-yín" (; 15th) month, etc. following the cycle. The 5th year will end with a "yǐ-chǒu" (; 2nd) month. The following month, the start of a "jǐ" or "jiǎ" year, will hence again be a "bǐng-yín" (3rd) month again. The beginning and end of the (solar) months in the table below are the approximate dates of current solar terms; they vary slightly from year to year depending on the leap days of the Gregorian calendar. The table above allows one to find the stem & branch for any given date.