Schedule Start/Stop time of internet radio on RPi1

Hello

I’m using Volumio ver 2.513 on Raspbery Pi 1B.
I would like to make automatic schedule of internet radio start and stop of playing.
It should play Mon-Fri 08:30-17:30.

First, I wanted to use Alarm function. I have made two playlists. First playlist contains address of stream of internet radio I would like to listen (stream.playradio.rs:8001/play.aac) and the second contains one mp3 song. I have made setting that first alarm starts at 08:30 (I have chosen first playlist) and the second alarm starts at 17:30 playing second playlist with mp3 song after which playing should be stopped until tomorrow morning at 08:30. But, there is some bug… It happens, randomly, that at 17:30 first playlist (instead of second) is started and internet radio starts playing again.
Time zone and time are set corretly using tzdata…

After that dead end I have tried to solve this using crontab. I have made crontabjob (crontab -e command). I have added Saturday playtime 9:30-13:05):

30 08 * * 1-5 mpc add http://stream.playradio.rs:8001/play.aac; mpc volume 60; mpc play; 30 17 * * 1-5 mpc stop; mpc clear 30 09 * * 6 mpc add http://stream.playradio.rs:8001/play.aac; mpc volume 60; mpc play; 05 13 * * 6 mpc stop; mpc clear

But, internet radio doesn’t stop at 17:30 and it doesn’t start at 08:30.
While I was testing crontab solution at short periods (5-10 minutes), it seemed to work as expected…
What could be solution for this?

Thanks in advance.