Based on DtTvB work, this is just an improved way for automatic usage. It also includes some bugfixes, improvements and fully compatible with IE8+. No third-party library dependency.

For a given id attribute of 'birthday', you should have

• an input text with id equal to 'birthday'
• an onclick event on it to show datepicker

<input 
	type="text" 
	name="date_button" 
	id="date_button" 
	value="2011-06-02" 
	onclick="ds_sh('date_button','date_button')"
>

Then, use ds_sh(id value, position) to use datepicker. First parameter is the ID value of the input element, second is the ID value of an element to use its X-Y position (could be any DOM element).

Position can also be an array with X & Y values as [10,40].

<input
	type="text"
	name="date_button"
	id="date_button"
	value="2011-06-02"
	onclick="ds_sh('date_button', [10,40])"
>

For a given id attribute of 'birthday', you should have

• 3 selects with ids 'birthday_day', 'birthday_month' & 'birthday_year'.
• an hidden input text with id equal to 'birthday'

<select
	name="date_select1_day"
	id="date_select1_day"
	size="1"
	onblur="ds_update('date_select1')"
>
	...
</select>
			
<select
	name="date_select1_month"
	id="date_select1_month"
	size="1"
	onblur="ds_update('date_select1')"
>
	...
</select>

<select
	name="date_select1_year"
	id="date_select1_year"
	size="1"
	onblur="ds_update('date_select1')"
>
</select>

<input
	type="hidden"
	name="date_select1"
	id="date_select1"
	value="2011-06-02"
>
<a
	href="javascript:ds_sh('date_select1','date_select1_dp')"
	id="date_select1_dp"
><img src="datepicker_cal.gif"></a>

If no valid date is given, everything blows, where it should use today date.

This code works fine, but it's a total mess. It should be an object and all functions should renamed for something that actually make sense.

A lot more comments wouldn't be luxury neither, responsive CSS and multilingual support would be pretty nice too!