This code places three Elementary Datetime widgets on a window, each of them exemplifying the widget's different usage.

The first of them is "only Date display":

   //datetime showing only DATE
   datetime = elm_datetime_add(bx);
   evas_object_size_hint_weight_set(datetime, EVAS_HINT_EXPAND, EVAS_HINT_EXPAND);
   evas_object_size_hint_align_set(datetime, EVAS_HINT_FILL, 0.5);
   elm_datetime_field_visible_set(datetime, ELM_DATETIME_HOUR, EINA_FALSE);
   elm_datetime_field_visible_set(datetime, ELM_DATETIME_MINUTE, EINA_FALSE);
   elm_datetime_field_visible_set(datetime, ELM_DATETIME_AMPM, EINA_FALSE);
   elm_box_pack_end(bx, datetime);
   evas_object_show(datetime);

For "only Time display", see the second datetime:

   //datetime showing only TIME
   datetime = elm_datetime_add(bx);
   evas_object_size_hint_weight_set(datetime, EVAS_HINT_EXPAND, EVAS_HINT_EXPAND);
   evas_object_size_hint_align_set(datetime, EVAS_HINT_FILL, 0.5);
   elm_datetime_field_visible_set(datetime, ELM_DATETIME_YEAR, EINA_FALSE);
   elm_datetime_field_visible_set(datetime, ELM_DATETIME_MONTH, EINA_FALSE);
   elm_datetime_field_visible_set(datetime, ELM_DATETIME_DATE, EINA_FALSE);
   elm_box_pack_end(bx, datetime);
   evas_object_show(datetime);

The third one will display datetime shows both Date and Time, corresponding format will be taken from system locale. Note, besides, that the strings are different for different language settings.

Datetime format can be programmatically set by using elm_datetime_format_set():

   //datetime showing both DATE and TIME
   datetime = elm_datetime_add(bx);
   evas_object_size_hint_weight_set(datetime, EVAS_HINT_EXPAND, EVAS_HINT_EXPAND);
   evas_object_size_hint_align_set(datetime, EVAS_HINT_FILL, 0.5);
   elm_box_pack_end(bx, datetime);
   evas_object_show(datetime);

The default format of any locale consists:

Year Field
Month Field
Date Field
Hour Field(12hr/24hr format)
Minute Field
AM/PM (if exists).

See the full source code for this example.