how to solve object has no attribute 'strftime'

Question

I've tried to strftime, but i have AttributeError Here is the code

dater=num2date(datafile.variables['lightning_flash_TAI93_time'][:], start_value_units.units)

        daty=dater.strftime("%Y%m%d")
        date = np.concatenate([date, daty[:]])

And error

File "ISS_LIS_FlashLoc_Quickview_Python3.py", line 154, in <module>
    main(file_path)
  File "ISS_LIS_FlashLoc_Quickview_Python3.py", line 97, in main
    daty=dater.strftime("%Y%m%d")
AttributeError: 'MaskedArray' object has no attribute 'strftime'

How i can solve it?