Is there a specific tag in html so as to make a field behave as a date picker in a form?
no such facility is there in html.
You may user jquery-ui, datepicker, its easy to use
Yes, in html5 there is:
<input type="date"> . But it's not really widely supported.
ok found using the jquery codes to show picker
@twiss: Its not html5 in my case, just a normal html form
There's also type=datetime, if that's what you want. Support of it: http://www.quirksmode.org/html5/inputs.html. Turns out only Chrome 10+ and Opera support it. IE10 will probably support it, but it will take a long time for people to use that.
Edit; browsers don't care about the doctype for this, but using a script is better indeed.