ODK Central API - Dates comparison seems to not working properly

1. What is the issue? Please be detailed.

I tried to import in MongoDB, a csv file received from ODK Central with the help of ODK Central API.
As I do not want to create a bunch of duplicate in my database, I tried to send a filtered request based on date comparaison.
The request sent, with Python, looks like that:

download = requests.get(central_url + "/v1/projects/6/forms/" + subname + "/submissions.csv.zip?$filter=__system/submissionDate gt {}".format(last_submission_final), auth=(central_email, central_password))

which is received by ODK Central:


I have exactly the same date in both ODK Central and the Mongo database:
I thought that the filter operator "gt" would skip to import the mongo document with the same date. But it seems not.
I always received a *.csv file with a line includind the date above.
It seems that the "gt" operators behave the same way that the "ge" one.

2. What steps can we take to reproduce this issue?

3. What have you tried to fix the issue?
For know, I will try to add a minute to the time sent. If it happens that the "lt" operator is responsible in my script issue.

4. Upload any test forms or screenshots below.

Does anyone encounter this kind of issue ?

It is a known issue, and there is a discussion going on to fix this.

Ref: https://github.com/getodk/central-backend/issues/459

Thanks for the reply. And apologizes for this useless topic ... I should have read more carefully the ongoing issue.
For now, I still use this kind of workaround:
last_submission_timeshift = last_submission_ugly + timedelta (seconds=10)