When the Gregorian calendar was adopted it caused some difficulty in the choice of season-words. As a result of this change of calendars many other old season-words that fit the luner caalender do not fit the new calendar, but we continue to use them. The number of season-words for Japanese haiku has never been constant, varying from tree to five thousand at different times and according to different authorities. We use a glossary of season-words to check whether a word can be used to denote a season. Because the saijiki is more helpful, it is more widely used.
Most haiku practitioners rely on a saijiki.
It usually takes a beginner five or six years to learn how to identify and use season-words properly. In the process, the consciousness of seasonal transition and its significance is deepened, and the student is introduced to a new and alluring realm of poetry. Saijiki are available in pocket edition, usually of five to six hundred pages. These contain the words that occur most frequently, usually limited to about fifteen hundred. Larger books contain two or three times that number.