Windows Auto Dark Mode

main.py

"""
Create windows task to run this script:

1) Add multiple triggers:
- at system startup
- at 9 AM every day (your desired time to disable dark mode)
- at 9 PM every day (your desired time to enable dark mode)

2) Add an action:
Action = Start a program
Program/script = <path to python3> (example: "D:\Python\Python-3.8.3\python.exe")
Arguments = <path to this script> (example: "D:\Auto-Dark-Mode\main.py")

3) Edit conditions:
Start the task only if the computer is on AC power = OFF

4) Edit settings:
Run task as soon as possible after a scheduled start is missing = ON
"""
import time
from subprocess import check_output

local_time = time.localtime(time.time())
current_hour = local_time.tm_hour
reg = "reg add HKCU\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize /v AppsUseLightTheme /t REG_DWORD /d {value} /f"
reg_value = 1

# your desired time to enable dark mode
if (
    (21 <= current_hour <= 23) or
    (0 <= current_hour < 9)
):
    reg_value = 0

reg = reg.format(value=reg_value)

check_output(reg)