The date 10/01/2018 is being returned on my template as 09/30/2018. As far as I can tell, the other dates seem to be fine, just this one date that I am aware of.
This thread looks to be about the same issue:
Survey123 Report dates off by one
It looks like it may be related to Daylight Saving Time. That could explain why the date after the time change is correct, but the date before is incorrect.