Possible to set 2 data fields within 1 select option?

Question

I have the following code in my form, but I'd like to also save the eventDate of the selected entry into a separate date field to enable sorting/selection later.

<label for="eventName">Event
<select id="eventName" name="fields[eventName]">  
  <option value="">select from list</option>
    {% set events = craft.entries.find({section:'events,activities', eventDate : ">= " ~ now.w3cDate() , order:'eventDate'}) %}
    {% if events %}
        {% for entry in events %}                
            <option value="{{ entry.eventDate.format('D j M') }},{{ entry.eventName }}">{{ entry.eventDate.format('D j M') }},{{ entry.eventName }}</option>
        {% endfor %}
    {% endif %}
</select>            
</label>

Answer 1

You could use the Preparse plugin to create a field that is automatically updated with the eventDate value whenever the entry is saved. It wouldn't be a datetime field, but if you stored the timestamp (i.e. {{ dateString|date('U') }}) it'd be easy to use as such.

Another option is to have an hidden input in your form for the eventDate datetime field, and use JavaScript to set its value whenever the <select> input changes (i.e. listen for the change event for the latter, in your JS).

The third option would be to write a plugin which listens to the entries.beforeSaveEntry event in order to set the eventDate value from the dropdown field.

Answer 2

As there was no simple answer that didn't require another plugin or javascript I revised my entry form to collect the date manually. Which is a bit of a pain, as the input format for the date has to be mm/dd/yyyy, which isn't normal in the UK.