code: def dateadd(value: fields.DateTime(),
              addend: fields.Int(validate=Range(min=1)),
              unit: fields.Str(validate=OneOf(['minutes', 'days']))='days'):
      
      value = value or dt.datetime.utcnow()
      if unit == 'minutes':
          delta = dt.timedelta(minutes=addend)
      else:
          delta = dt.timedelta(days=addend)
      result = value + delta
      return {'result': result}
docs: Add a value to a date.