The function fillDays is making an wrong comparison, because when calls the function isDateBigger, it passes the minDate with the correct time and the current date (from iteration) with time 00:00. This is a problem, because if minDate is "2019-05-27 00:10", in some iteration of fillDays, the current date will be "2019-05-27 00:00" (same date, but with wrong time), thus isDateBigger will treat minDate as a bigger date, disabling the day "2019-05-27".
This can easily be resolved passing all days to isDateBigger, in fillDays, with the same time as minDate.
The function fillDays is making an wrong comparison, because when calls the function isDateBigger, it passes the minDate with the correct time and the current date (from iteration) with time 00:00. This is a problem, because if minDate is "2019-05-27 00:10", in some iteration of fillDays, the current date will be "2019-05-27 00:00" (same date, but with wrong time), thus isDateBigger will treat minDate as a bigger date, disabling the day "2019-05-27".
This can easily be resolved passing all days to isDateBigger, in fillDays, with the same time as minDate.