Although all my notes and early manuscript versions said March 23, somehow the book ended up with an April 7 date on page 161 for Esteban’s departure from Vacapa. He actually left on March 23, 1539. The March 23 date is accurately cited in "Noteworthy dates" on page xv.
It was Friar Marcos who left on April 7, as the book states two pages later.
By the way, all dates in the Spanish chronicles of the 1500s are by the Julian calendar in effect then. To convert from the Julian calendar to today’s Gregorian calendar, 10 days must be added.