Some people consider holiday seasons as a contributor for bitcoin and altcoin value.  In broader sense, investors attitude toward seasons might be a factor but logically do not barely lies on it.  The deflation of bitcoin value for the first month of January is due to the correction of price due to very high price bitcoin reach on the early week of December plus the bad rumors, news and speculations regarding bitcoin affect bitcoin value on the preceding days.  Last Chinese New Year, we experienced a bit increase in bitcoin value because bitcoin started to gain trust again from its investors because negative news and speculations regarding cryptocurrency stops.