Python3 script that reminds you how many days passed since the given date. (No 3rd party library dependencies)

date_alarm.py

#!/usr/bin/env python3

import time
from datetime import datetime, timezone, timedelta
import requests
import traceback

####################################################
# SET THOSE VALUES

MENTION = "@here"
START_DATE_STRING = "2023-01-01"
DISCORD_WEBHOOK = "your-discord-webhook-url"
ALERT_UNTIL_BEFORE = 7
SPECIAL_DATE_MESSAGES = {
  "05-21": {
    "match": "5/21 is your birthday",
    "before": "{} days left until your birtuday(5/21)",
  },
}

####################################################

TIMEZONE = timezone(timedelta(hours=9))
START_DATE = datetime.strptime(
  START_DATE_STRING, "%Y-%m-%d"
  ).astimezone(TIMEZONE)

def retry_n_times(func, sleep_secs=5, n=3):
  tries = 0
  while True:
    try:
      return func()
    except Exception as e:
      if tries < n:
        tries += 1
        time.sleep(sleep_secs)
      else:
        raise e

if __name__ == "__main__":
  MESSAGE = ""
  DEFAULT_MESSAGE = ""
  ADDITIONAL_MESSAGE = ""

  today = datetime.now(tz=TIMEZONE)
  day_diff = (today - START_DATE).days + 1

  DEFAULT_MESSAGE = f"It has been {day_diff} days passed since {START_DATE_STRING}."

  for date_key, date_message in  SPECIAL_DATE_MESSAGES.items():
    date_key_date = datetime.strptime(f"{today.year}-{date_key}", "%Y-%m-%d").astimezone(TIMEZONE)
    day_diff = (date_key_date - today).days + 1

    if date_key_date.month == today.month and \
      date_key_date.day == today.day:
      ADDITIONAL_MESSAGE += f"\n- {date_message['match']}"
    elif 0 < day_diff <= ALERT_UNTIL_BEFORE:
      ADDITIONAL_MESSAGE += f"\n- {date_message['before'].format(day_diff)}"

  def sender():
    MESSAGE = (f"{MENTION}\n" if len(ADDITIONAL_MESSAGE) > 0 else "") \
      + DEFAULT_MESSAGE \
      + ADDITIONAL_MESSAGE
    data = {
      "content": MESSAGE
    }
    res = requests.post(DISCORD_WEBHOOK, json=data)
    res.raise_for_status()

  try:
    retry_n_times(sender)
  except Exception as e:
    traceback.print_exc()
    print(MESSAGE)

Crontab example

30 8 * * * /your/script/directory/date_alarm.py >> /your/log/directory/date_alarm.log