Date Format change on XSLT

Hi Team, 

Currently i have a  requirement to convert to  datetime format on the xslt level, Could you please support to sort out my concern,

Current mapping output-

<LocalProcessing>
<DeliveryRequiredBy>20191021</DeliveryRequiredBy>
</LocalProcessing>

Required format-:

<LocalProcessing>
<DeliveryRequiredBy>2019-10-21T00:00:00.00</DeliveryRequiredBy>
</LocalProcessing>