Format for time display?

Try using

->add('fromDate','datetime',array('date_format' => 'yyyy-MM-dd HH:mm:ss'))

By the way, the relevant code is here. I think your format option gets overwritten by the system, so it's important to use date_format instead. For an application-wide solution, have a look at this question too.

Nothing from the above had worked for me, so I ventured to inspect the page source, which pointed me towards template used:

<!-- START
    fieldName: date
    template: SonataAdminBundle:CRUD:list_date.html.twig
    compiled template: SonataAdminBundle:CRUD:list_date.html.twig
    -->
<td class="sonata-ba-list-field sonata-ba-list-field-date" objectId="1">11.03.17</td>
<!-- END - fieldName: date -->

And after inspecting the template I've found the correct option filed name:

{%- elseif field_description.options.format is defined -%}

So I made my Admin code like this

->add('date', null, ['format' => 'd/m/Y'])

and it worked.

Note that format is the regular date() format, and one have to use just a single placeholder mark, like y for year, as yyyy produces 2017201720172017.

If you use SonataIntlBundle then date formats are:

$list->add('createdAt', 'date', array(
    'pattern' => 'yyyy-MM-dd',
))

described in https://sonata-project.org/bundles/intl/master/doc/reference/datetime.html