I tried to use crontab on Mac but it didn’t work so I learned how to use launchd. Here is how:
1. Create a plist file under your ~/Library/LaunchAgents folder and make sure it named something like "test1.plish".
2. sudo chmod 600 test1.plish
3. sudo chown root test1.plish
4. sudo launchctl load -w test1.plish

You can stop the demon by:
sudo launchctl unload test1.plish.

Another thing I learned afterwards is the environment of daemon is different from yours. So you need to use absolute path when calling commands that are not available in daemon’s path.