31 * 01,03 01/2 *
01/2-01,03 *:31
What's the point of your gripes? Would you really suggest to someone, who has a systemd-based distro, to spin up systemd-cron or cronie and keep writing crontabs? Do you have some specific complaint about systemd calendar syntax that you think could be improved? 0 0 ? * fri#3 (special syntax is needed because cron uses logical-or to combine day and weekday fields)
or systemd fri *-*-15..21 (works because systemd day and weekday are joined with logical-and)
[cf] https://developers.cloudflare.com/workers/configuration/cron...