Datepicker on modal - incorrect position calculation

''L ~7680:''

inst.dpDiv.css({position: ($.datepicker._inDialog && $.blockUI ?
'static' : (isFixed ? 'fixed' : 'absolute')), display: 'none',
left: offset.left + 'px', top: offset.top + 'px'});

The offset here (specifically top) is not being calculated correctly when the datepicker is embedded on a modal. If the user scrolled down the page a little bit before opening the modal, then the datepicker is rendered, it is positioning the datepicker along the Y axis of the page much further down than appropriate.

I believe this is caused by these lines here:

''L ~7324:''

var scrollX = document.documentElement.scrollLeft || document.body.scrollLeft;
var scrollY = document.documentElement.scrollTop || document.body.scrollTop;
this._pos = // should use actual width/height below
[(browserWidth / 2) - 100 + scrollX, (browserHeight / 2) - 150 + scrollY];

My solution, however hack-ish, was to change L ~7682 from

left: offset.left + 'px', top: offset.top + 'px'});

to

left: ($(".ui-datepicker-trigger:visible").offset().left + 28) + 'px', top: ($(".ui-datepicker-trigger:visible").offset().top - document.body.scrollTop) + 'px'

Where :visible is used because in our project we have multiple ui-datepicker-trigger's (the unused ones being hidden via display:none). I believe the use of document.body.scrollTop is paramount versus document.documentElement.scrollTop because of how the modal is rendered.