In the nostr:npub1tr0va8lk35pp4lnk64ymneywdjmmq6juznxlg5ejerkhxgwk7ggsw5qqpx episode with nostr:npub13sajvl5ak6cpz4ycesl0e5v869r5sey5pt50l9mcy6uas0fqtpmscth4np, they mentioned an opensource calendar software, but I couldn't understand its name. I'd appreciate any help or pointers to it, please? :-)