|saison filter, applied to a tag that returns a valid date, displays the common name of the corresponding season (summer, autumn...).
Example: for an article published on 22-01-2008,
[(#DATE|saison)] will display "winter".
The seasons are defined as:
- from 21-03 to 20-06: spring
- from 21-06 to 20-09: summer
- from 21-09 to 20-12: autumn
- from 21-12 to 20-03: winter