How to set date format for polyfilled date input?

[ConanVF67]

I'm using Polyfils to support legacy browsers in my HTML5 app. One feature I'm really interested in is \[code\]<input type="date">\[/code\] with native date picker. However js-based fallback date picker polyfils gave me uses different (localized?) date format. The date field is filled correctly (2012-12-24), but the generated text input visible to user shows date in like this: "24.12.2012". How to force it to display date in YYYY-mm-dd?