The dateITA does not validade dates when the date it´s the begging of DST.

For example (in Brazil) the Date 16/10/1966 fails.

When you analyze the date, the var gg is set to 16 but new Date(1966,9,16) returns Date {Sat Oct 15 1966 23:00:00 GMT-0300}.

So when you compare xdata.getDate() == gg (at line 143) it fails because gg is 16.

A workaround I'm using is to change the line 143

if ( ( xdata.getFullYear() == aaaa ) && ( xdata.getMonth () == mm - 1 ) && ( xdata.getDate() == gg ) )

to

if ( ( xdata.getUTCFullYear() == aaaa ) && ( xdata.getUTCMonth () == mm - 1 ) && ( xdata.getUTCDate() == gg ) )

so the DST is ignored. I admit : I didn´t do a good test with older browsers.

Does it makes sense?

BTW, great plugin!