You're part way there. Make the "time" axis Discrete. Then right-click on that axis, and in the pop-up menu, select "Show missing values". Tableau will fill in the gaps.
Is that what you're looking for?
I treated the timestamp as "Attribute".
But the "Show missing values" item is not visible if I treat the timestamp as "Attribute".
Why I treated timestamp as an attribute?
Because I want to display the timestamp in format (Month, Day - Hour). Example: Jul 3 - 12
and I make it via Format->Custom and under Custom I typed: mmm dd - hh.
If I uncheck the "Attribute" then my formatting options are Year/Month.Quoter/DayHour/Custom.
Under "Custom" I see the following dialog which is different from the previous one and I do not see how to
achieve the formatting (Month Day - hour)
Probably I do not understand the difference between "attribute" and non-attribute.