4
If they don't allow cron then cron won't run..
XOOPS isn't an engine that runs without user browsing. Some hosters allow cron via cPanel or something.
However, an untested trick might be to create a custom block that calls your script. The script would need to check the clock to know if it should run and that it hasn't already run. The block might not need to output any info (invisible), just need to call your script.
BTW, any server still allowing telnet would be very surprising. Hard enough to get an SSH console these days.