Jcal have a bug in Debian 12 which show wrong day of month. But it fixed in newer releases.
To use newer version on Debian 12, download compiled binary from here
Remove old version from debian 12
$ sudo apt purge jcal
Extract archive and place binary executable to a location which $PATH can read
$ tar xvf jcal.tar.gz
$ cd jcal
$ sudo cp /usr/local/bin
From now you can use updated version of jcal without error.
$ jcal
Dey 1404
Sh Ye Do Se Ch Pa Jo
1 2 3 4 5
6 7 8 9 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28 29 30
Also you can use aliases in bash
alias now_t='date +'\''%A %T '\'' ; now ; now_j'
alias now='date '\''+%Y_%m_%d'\'''
alias now_j='jdate '\''+%q %Y_%m_%d'\'''