Do you really want " I want the last hour of September 29th to connect with the first hour of Sepetmber 28th."
Did you mean " I want the last hour of September 28th to connect with the first hour of Sepetmber 29th."?
For continuous plots involving date and time I would ensure that I had a SAS date time variable.
You could make a datetime variably using the DHMS function:
DT = DHMS(date, hour,0,0);
in a data step.
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