I added 24h to the stop time and that gets the correct date:
2 2018-12-28 04:17:09.755 debugtimeWindowStop = Sat Dec 29 07:14:00 EST 2018 adjusted: Sat Dec 29 07:14:00 EST 2018
app:5602018-12-28 04:17:09.754 debugtimeWindowStop = Sat Dec 29 07:16:00 EST 2018 adjusted: Sat Dec 29 07:14:00 EST 2018
app:5602018-12-28 04:17:09.749 debugtimeWindowStart = Fri Dec 28 17:37:00 EST 2018
app:5602018-12-28 04:17:09.747 debugdaysOk = true
app:5602018-12-28 04:17:09.746 debugmodeOk = true
app:5602018-12-28 04:15:09.642 debugInstalled with settings: [frequency_minutes:17, number_of_active_lights:1, switches:[Living Dimmer, Dining Light, Hall Front Light, Bed Front Dimmer, Bed Side Dimmer, Master Bed Dimmer, Master Bath Light, Kitchen Dimmer, Bathroom Light], newMode:[Away], startTimeType:sunset, starting:2018-12-28T00:01:00.000-0500, endTimeType:sunrise, endTimeOffset:1440, people:[A, D]]
Tried starting 24h earlier: works fine.