setdateTime fails occasionally for seconds

[rrelande]

Thanks for a great library

Wire.begin(5, 4);
rtc.begin();
rtc.setDateTime(2019, 4, 1, 12, 33, 59);

taking the example code,
I've noticed that function will occasionally misread the example date and time. Instead of :59 (seconds) it will set :00 seconds, creating a 59 second gap. sometimes it will succeed though and write the right time.

This is just a random discovery hopefully no further issues.

[rrelande]

The output on Serial is the below: (5s delay between set call and display call:
occasionally this:
Setting time RTC time to 2019 april 1 12:33:59
RTC time: 2019-4-1/12:33:0

Occasionally this:
Setting time RTC time to 2019 april 1 12:33:59
RTC time: 2019-4-1/12:34:4

[rrelande]

after testing with other PCF8563 library, the same issue is applicable
it seems not related to this library only.