error related to date string

[oneEyedCharlie]

I get:

user@computer:~/folder/moon-phase-background-main$ ./moonback.sh
./moonback.sh: line 12: 200*24-24+09: value too great for base (error token is "09")
./moonback.sh: line 19: 200*24-24+09: value too great for base (error token is "09")
curl: Remote file name has no length!
curl: (23) Failed writing received data to disk/application
composite-im6.q16: missing an image filename `back.tif' @ error/composite.c/CompositeImageCommand/1616.
/home/user/folder/moon-phase-background-main
rm: missing operand

I don't know how to fix that. But I do love this idea, and thank you for it.