title: I want to store datetime in peewee.DateTimeField(), I use datetime.datetime.now() in that field as default but it can't work
body: <p><strong>this code cannot work and give json serializable error</strong></p>
  
  <pre><code>  class Bank(peewee.Model): // create Bank table
          bank_id     = peewee.PrimaryKeyField()
          bank_name   = peewee.CharField()
          account_no  = peewee.CharField()
          ifc_code    = peewee.CharField()
          swift_code  = peewee.CharField(null = True)
          modify_date = peewee.DateTimeField(default=datetime.datetime.now(),formats=['%Y-%m-%d'])/*date in yyyy-mm-dd formate*/
          status      = peewee.IntegerField(default = 0)
  
          class Meta:
              database = db
  </code></pre>