Lack of 'no date set' info
I'm not sure if this is a bug, but when calendar field don't have set recurrent data or time period options, and entry is saved without data in this field, then such field don't show 'no date set' message in the entry view. Example XML data for three calendar fields:
<field_standard_date id="5" itemprop="" type="calendar" suffix="" position="2" css_view="spClassViewCalendar" css-view="spClassViewCalendar" css_class="spClassCalendar" css-class="spClassCalendar">
<label lang="en-GB" show="1">Standard date</label>
<data></data>
</field_standard_date>
<field_recurrent_date id="6" itemprop="" type="calendar" suffix="" position="3" css_view="spClassViewCalendar" css-view="spClassViewCalendar" css_class="spClassCalendar" css-class="spClassCalendar">
<label lang="en-GB" show="1">Recurrent date</label>
<data lang="en-GB" class="spClassCalendar" timestamp="0" startdate="0" enddate="0" offset="0">no date set</data>
</field_recurrent_date>
<field_time_period id="7" itemprop="" type="calendar" suffix="" position="4" css_view="spClassViewCalendar" css-view="spClassViewCalendar" css_class="spClassCalendar" css-class="spClassCalendar">
<label lang="en-GB" show="1">Time period</label>
<data lang="en-GB" class="spClassCalendar" timestamp="0" startdate="0" enddate="0" offset="0">no date set</data>
</field_time_period>Tested with ver. 2.2.0.10