Odoo shows dates with timezone. 

In your database time is UTC+0 (if you haven't re-configured it). Thus, when you write to PostgreSQL using the API, you write date without any timezone. When you open a view time is shown according to your local timezone.

In order to fix it, you should substract the difference while making a request. Based on your examples, you should write time with an hour substracted. You can achieve that by converting your date strings into Python datetime and by using the Python timedelta. For more details regarding the Python datetime package have a look at this article - https://docs.python.org/3/library/datetime.html