I'm taking a look at the Tabler AppScript..I never changed anything since I started to run it, so there might be a hidden bug.

I believe it's a bug due to daylight saving changes.
We are currently adding 1000*60*60*24*(# of days to Monday) to the current datetime, to get the Monday's date.
However, we are 1hrs more away to Monday due to daylight savings now...
That's why the script calcualted "Sun Nov 06 23:00:00 GMT-08:00 2016" instead of Monday at 00:00:00.

Reference: the current function
function CalculateNextMonday() {
    var d = new Date();
    d.setHours(0, 0, 0, 0);
    var n = d.getDay();
    var days = 0;
    if (n == 0) {
        days = 1;
    }
    else {
        days = 8 - n;
    }
    return new Date(d.getTime() + (1000*60*60*24*days));
}

+stip, he knows why :)

That's weird, I thought AppScript was executing in PST context and so daylight saving's time wouldn't affect it (until next week)?

Should we hedge our bets and add 60*60*2 (2 hours) to pad and hopefully avoid this in the future?

No longer on the Chrome team, e-mail me @google.com if any attention still required from me here, otherwise good luck!