title: Rails & Postgres: Migration to change_colomn gives error "cannot be cast to type timestamp without time zone"
body: <p>A Rails migration to turn a "deleted_at" time column to a datetime column failed. Any ideas on how to solve this? It's a fresh install of Postgres if that is relevant.</p>
  
  <pre><code>-- change_column(:products, :deleted_at, :datetime)
  
  
   PGError: ERROR:  column "deleted_at" cannot be cast to type timestamp without time zone
  : ALTER TABLE "products" ALTER COLUMN "deleted_at" TYPE timestamp
  </code></pre>