Coordination activities follow a timeline, which includes various deadlines, as published in the WASG.
The scheduling calendar is based on two scheduling seasons, Summer and Winter, defined as follows:
IATA Summer Season - starts on the last Sunday of March and ends on the last Saturday of October (where the following Sunday is still in October)
IATA Winter Season - starts on the last Sunday of October and ends on the last Saturday of March (where the following Sunday is still in March)