Based on my calculations ...
In the past 21 months, the schedule has been "made available" an average of 52.5 days in advance.
In the past 12 months, the schedule has been "made available" an average of 51.4 days in advance.
In the past 6 months, the schedule has been "made available" an average of 45 days in advance.
In the past 3 months, the schedule has been "made available" an average of 30.3 days in advance.
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In the past 20 months, there has been an avaerage of 32.3 days between "new month announcements".
In the past 12 months, there has been an avaerage of 32.2 days between "new month announcements".
In the past 6 months, there has been an avaerage of 36.3 days between "new month announcements".
In the past 3 months, there has been an avaerage of 42 days between "new month announcements".
Of course, it is difficult to use this data to predict the future because the data trends towards, for example, making an announcmenet in November that October has just become available. But that is what the all-powerfull spreadsheet says.