Calculate Date field in ArcPy

I'm trying to use arcpy.ExtractValuesToPoints() to get raster values to a points feature class for several raster files (8760). The goal is to get a time-slice view of how the values at certain locations change over time.

I'm fairly well versed in Python as well as the built-in datetime module. The trouble that I'm having is saving the date-time values to a table in ArcGIS.

(I've gotten a similar approach to work using arcpy.da.InsertCursor() but this approach is very process-intensive and I've concluded that it isn't a viable approach for what I'm trying to do. Plus I'd rather not re-invent the wheel and use the ArcGIS function: ExtractValuesToPoints() instead.)

To give a little background, I'm using dates that require datetime precision to the hour so I've elected to use a File Geodatabase to accommodate that feature (since shapefiles can only handle the date portion).

I'm trying to solve for a single case as I can create a solution for iterating over the 8760 files that I'm working with.

So far this is what I have:

import arcpy
import os

GRID_Table = "E:\HRRR.gdb\GRID_Table"               # GRID_Table is an ArcGIS table
SPP_LMP_Points = "E:\HRRR.gdb\SPP\SPP_LMP_Points"   # that contains datetime and                  
out_path = "C:\scratch.gdb"                         # raster_path pairs.


row1 = []                                           # Get date_time and raster_path      
for row in arcpy.SearchCursor(GRID_Table):          # from every entry in GRID_Table
    row1.append((row.DateTime, row.RasterPath))     #

date_time = row1[0][0]                              # Set date_time to the first 
raster_path = row1[0][1]                            # entry 

out_path_shp = os.path.join(out_path, os.path.basename(raster_path))  # Generate 
                                                                      # output path.

arcpy.sa.ExtractValuesToPoints(SPP_LMP_Points, raster_path, out_path_shp)

arcpy.AddField_management(out_path_shp, "DateTime", "DATE")

arcpy.CalculateField_management(out_path_shp, "DateTime", 
                                "!DateTime! = {0}".format(date_time), 
                                "PYTHON_9.3")

This all works fine and doesn't report any exceptions or errors. The trouble that I'm having is that the call to arcpy.CalculateField_management() doesn't populate the DateTime field. Instead I get a NULL value in the table.

Any thoughts?