The depalatalization of consonants preceding e and ä took place later, thus the frequency of occurrence of palatalized consonants was lowered, but it strengthened the palatalization contrast at the same time. The change of ’ä > ě and ä > a took place at the end of the 12th century.
The palatalization of consonants preceding e and ä occurred later, so the frequency of palatalized consonants decreased, but it intensified the contrast in palatalization at the same time. The change from ’ä to ě and ä to a happened towards the end of the 12th century.