Using arcpy and script toolbox to add the date to a attribute table

Question

I would like some information on how to add a date to an attribute table, by adding a user specified date in a script tool that will update the polygons attribute table. In short I have two polygons that I wish to calculate the difference in time, in hours between them. The date is determined by specification inside a script box, seen in the image below.

I would like to use code that goes along with my tool and I need to figure out what I'm missing in the following code; (This is the simple code for the tool)

import arcpy 

Mother1 = sys.argv[1]
date1= sys.argv[2] ### I believe date style is in format mm/dd/yyyy hh:mm:ss 
Mother2 = sys.argv[3]
date2 = sys.argv[4]

try:
    arcpy.AddField_management(Mother1,"Date","DATE","#","#","#","#","NULLABLE","NON_REQUIRED","#")
    arcpy.AddField_management(Mother2,"Date","DATE","#","#","#","#","NULLABLE","NON_REQUIRED","#")

Then, I tried adding the date to the field such as this;

arcpy.CalculateField_management(Mother1, "Date", date1)
arcpy.CalculateField_management(Mother2, "Date", date2)

But that did not work.

I would like to add the date to the attribute table and then also be able to calculate the difference between the two dates, but need to get the date into the attribute table before I can calculate anything?

Answer 1

I would not assume it is a date. I would make sure the date and time is captured as a string and create a python expression using the strptime function and use a PYTHON_9.3 calculation to have the entire date and time calculated. VB Date expressions should be in the format of #date#, but they are not reliable, since they only preserve the date, not the time, and you cannot control how they interpret different string date formats, like you can with the strptime function using a PYTHON_9.3 field calculation. (Edit: I adjusted the try block location to make sure that any date conversion error is handled in the except block and I added logic to determine if the Date field should be added or if it already exists). The revised code now formats the strptime function expression as a string that allows the Field Calculator to do the date conversion using the strptime function, not the script:

import arcpy

from datetime import datetime

try:

    Mother1 = arcpy.GetParameterAsText(0)
    print arcpy.GetParameterAsText(1)
    ### Confirm from print that date string is in the format yyyy-mm-dd hh:mm:ss
    ### Make a Field Calculation expression that will use strptime to get a datetime. 
    date1 = "datetime.datetime.strptime('" + arcpy.GetParameterAsText(1) + "', '%Y-%m-%d %H:%M:%S')"
    ### VB Script calculations use "#date#" strings to create dates, but not datetime 
    ### date1 = '#' + arcpy.GetParameterAsText(1) + '#'
    Mother2 = arcpy.GetParameterAsText(2)
    date2 = "datetime.datetime.strptime('" + arcpy.GetParameterAsText(3) + "', '%Y-%m-%d %H:%M:%S')"
    ### VB Script calculations use "#date#" strings to create dates, but not datetime
    ### date2 = '#' + arcpy.GetParameterAsText(3) + '#'

    fields = arcpy.ListFields(Mother1)
    addfield = True
    for field in fields:
        if field.name.upper() == "DATE":
            addfield = False
    if addfield:
        arcpy.AddField_management(Mother1,"Date","DATE","#","#","#","#","NULLABLE","NON_REQUIRED","#")

    fields = arcpy.ListFields(Mother2)
    addfield = True
    for field in fields:
        if field.name.upper() == "DATE":
            addfield = False
    if addfield:
        arcpy.AddField_management(Mother2,"Date","DATE","#","#","#","#","NULLABLE","NON_REQUIRED","#")

    arcpy.CalculateField_management(Mother1, "Date", date1, "PYTHON_9.3")
    arcpy.CalculateField_management(Mother2, "Date", date2, "PYTHON_9.3")
except Exception as e:
    print e.message

    # If using this code within a script tool, AddError can be used to return messages 
    #   back to a script tool.  If not, AddError will have no effect.
    arcpy.AddError(e.message)