How to make a notification at a specific time?

Question

Android

Task:
Implement sending notifications at a certain time of the day, or rather Sunrise and Sunset.
Problems I ran into:
1. Determining sunrise and sunset times based on the user's location and saving it for later use.
1.1. How to store ?Where is it better to store ?DB, file?
1.2. How to determine the time of sunrise and sunset?
2. Sending a notification at a specific time
2.1. How to pull up and use data from a file, DB?
2.2 How to send notifications at a specified time?

Answer 1

1.1. It is possible even to store in SharedPreferences. tinyw.in/Gxjx1.2
. https://en.wikipedia.org/wiki/%D0%A3%D1%80%D0%B0%D... - short and clear.
2.1. tinyw.in/Gxjx2.2
. Use WorkManager. https://bit.ly/31tKRLl