The selection of the quietest days (Q-days) and most disturbed days (D-days) of each month is deduced from the Kp indices on the basis of three criteria for each day: . ... In order to indicate such a situation, selected days which do not satisfy certain absolute criteria are marked as follows. ... A selected disturbed day is considered not really disturbed and marked by an asterisk ( * ) if Ap less than 20. ... January 2000 - recent . January 1990 - December 1999 . ...