Here is a message from Sony Interactive Entertainment America marketing vice president Asad Qizilbash regarding the delay:
We want to share a change in release date for this highly anticipated title from Bend Studio. We recently decided to move the release of Days Gone from the crowded February time frame to April 26, 2019. While the studio is eager to see Days Gone in the hands of fans, Bend Studio will take the opportunity to further polish Days Gone.
As PlayStation fans already know, Days Gone is an open-world action game set in the high-desert of the Pacific Northwest. Traversing harsh landscapes on their drifter bike, players must fight for resources as they attempt to survive broken roads, unpredictable weather, attacks from other human factions, infected wildlife and roaming Freakers — a brutal, dynamic world that is dangerous both day and night.
Days Gone will be released for PlayStation 4.