A note in the Introduction, regarding the Dates, states that
"The Calendar begins with Easter, and for the year 1912-1913, when it was first published, Easter Sunday fell on 7 April, so that the first week is dated 7-13 April. For this dating the other fixed festivals of the year, Midsummer, Michaelmas and Christmas, fell within the appropriate weeks. Easter however is still variable, and to begin the Calendar every year with Easter Sunday would sometimes bring it badly out of step with the other fixed festivals. It is therefore probably best to begin each year with the Sunday nearest to the original dating, but to regard the first verse (Easter Mood) as informing the whole Easter month."
In this light, Steiner offers the following for April (trans. by John Thomson)
When from the vastness of this world
The sun speaks to the human mind
And joy from the depths of soul
In beholding joins with light;
Then thoughts that burst from out the self
Stream into distant space
The human being with the Spirit's life.
Wenn aus den Weltenweiten
Die Sonne spricht zum Menschensinn
Und Freude aus den Seelentiefen
Dem Licht sich eint im Schauen,
Dann ziehen aus der Selbstheit Hülle
Gedanken in die Raumesfernen
Und binden dumpf
Des Menschen Wesen an des Geistes Sein.