Calculate date field using date variable and time attribute in a feature class

Question

I have a string variable (fileDateString) with the date in this format: 20150404

In my feature class there is a text field with time in twenty-four hour UTC format. There is also 2 leading spaces before the time. E.g. " 1300"

I have added a Date field to my feature class and I would like to calculate a date/time. I also want to be able to subtract 6 hours from the date/time (convert UTC to CST) for the final result.

I thought about first creating a text field with the date and time, then converting that to date but am wondering if there is an easier way?

expression = "\"" + str(fileDateString) + "\"" + "!DateUTC!"

Answer 1

Based on the requirements you described, the following Python expression should do what you're looking for:

"datetime.datetime.strptime({} + !date1!.strip(), '%Y%m%d%H%M') - datetime.timedelta(hours=6)".format(repr(fileDateString))

Note: I'm assuming months before days in your string. If not switch the %m and %d.