Datepicker not working on Visualforce Page When standardStylesheets="false"

Question

I want to disable standard stylesheets for a Visualforce page, but when I disable it, apex:inputfield does not provide date picker for date fields.

<apex:page standardcontroller="Opportunity" standardStylesheets="false">
    <apex:form>
        <apex:inputField value="{!Opportunity.Name}"/>
        <apex:inputField value="{!Opportunity.CloseDate}"/>
    </apex:form>
</apex:page>

When standardStylesheets are enabled it works fine.

Answer 1

With standardStyleSheets="true", SFDC generates HTML markup that includes

<div class="datePicker" id="datePicker" style="display: none; left: 230px; top: 42px;"><div class="dateBar"><img src="/img/s.gif" alt="Previous Month" class="calLeft" onblur="this.className = 'calLeft';" onclick="DatePicker.datePicker.prevMonth();" onfocus="this.className = 'calLeftOn';" onmouseout="this.className = 'calLeft';" onmouseover="this.className = 'calLeftOn';" title="Previous Month"><select id="calMonthPicker" name="calMonthPicker" title="Month"><option value="0">January</option>
<option value="1">February</option>
<option value="2">March</option>
<option value="3">April</option>
<option value="4">May</option>
<option value="5">June</option>
<option value="6">July</option>
<option value="7">August</option>
<option value="8">September</option>
<option value="9">October</option>
<option value="10">November</option>
<option value="11">December</option>
</select><img src="/img/s.gif" alt="Next Month" class="calRight" onblur="this.className = 'calRight';" onclick="DatePicker.datePicker.nextMonth();" onfocus="this.className = 'calRightOn';" onmouseout="this.className = 'calRight';" onmouseover="this.className = 'calRightOn';" title="Next Month"><select id="calYearPicker" name="calYearPicker" title="Year"><option value="2018">2018</option>
<option value="2019">2019</option>
<option value="2020">2020</option>
<option value="2021">2021</option>
<option value="2022">2022</option>
<option value="2023">2023</option>
<option value="2024">2024</option>
</select></div><div class="calBody"><table class="calDays" border="0" cellpadding="0" cellspacing="0" id="datePickerCalendar"><tbody><tr><th class="dayOfWeek" scope="col">Sun</th><th class="dayOfWeek" scope="col">Mon</th><th class="dayOfWeek" scope="col">Tue</th><th class="dayOfWeek" scope="col">Wed</th><th class="dayOfWeek" scope="col">Thu</th><th class="dayOfWeek" scope="col">Fri</th><th class="dayOfWeek" scope="col">Sat</th></tr>
<tr class="calRow" id="calRow1"><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekend prevMonth">30</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday">1</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday">2</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday">3</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday">4</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday">5</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekend">6</td></tr>
<tr class="calRow" id="calRow2"><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekend">7</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday">8</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday">9</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday">10</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday">11</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday">12</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekend">13</td></tr>
<tr class="calRow" id="calRow3"><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekend">14</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday">15</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday">16</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday todayDate">17</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday">18</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday">19</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekend">20</td></tr>
<tr class="calRow" id="calRow4"><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekend">21</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday">22</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday">23</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday">24</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday">25</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday">26</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekend">27</td></tr>
<tr class="calRow" id="calRow5"><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekend">28</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday">29</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday">30</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday">31</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday nextMonth">1</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekday nextMonth">2</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);" class="weekend nextMonth">3</td></tr>
<tr class="calRow" id="calRow6" style="display: none;"><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);">&nbsp;</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);">&nbsp;</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);">&nbsp;</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);">&nbsp;</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);">&nbsp;</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);">&nbsp;</td><td onblur="hiOff(this);" onclick="DatePicker.datePicker.selectDate(this);" onfocus="hiOn(this);" onmouseout="hiOff(this);" onmouseover="hiOn(this);">&nbsp;</td></tr>
</tbody></table><div class="buttonBar"><a href="javascript:%20void%280%29%3B" class="calToday" onclick="DatePicker.datePicker.selectDate('today');return false;">Today</a></div></div></div>

with standardStyleSheets="false", the div is not generated at all

The VF documentation states:

If you don’t load the Salesforce style sheets, components that require them don’t display correctly.

So, you'll need to use your own datePicker from some Javascript library. The book VisualForce Development Cookbook 2nd edition by the esteemed Keir Bowden aka Bob Buzzard, chapter 3 "Adding a custom datepicker" shows how to do this. This is a great book for VF developers who aren't using Aura or LWC.

The purpose of standardStyleSheets="false" is for applications that want total control over the look-and-feel (CSS) of the page.