Hey there .. i'm not sure if it is a specific Titanium problem or if some experienced something similar in 'normal' javascript .. i didn't ..
basically i'm trying to calculate a time difference .. and
narrowed the problem down to:
the javascript 'getTime()' function returns NaN for a Date parsed from string ..

so somewhere in my app i do this

Ti.App.Properties.setString('lastStateDate') = JSON.stringify(new Date());

and on the next startup i'll check for the value

var v_string = Ti.App.Properties.getString('lastStateDate');
var now = new Date();
var last = new Date(v_string);
if(now instanceof Date && last instanceof Date){
    //everything ok until here.
    var diff = now.getTime() - last.getTime();
    ....
}

(i removed all the if and elses for testing for undefined and null values and stuff .. so thats not the problem .. meaning the value of 'v_string' is a valid datetime string .. even 'last' has the correct value)

So any help or hint is appreciated
Greetz Katja

PS: ipad, sdk 1.7.5, ios 5.0