Not actually pcal's fault. Last time we sorted out how to get pcal to refer to the month after this month. But today the command line pcal -l -m -Pletter $((`date +%m` % 12 + 1)) $(date -d"next month" +%Y) | ps2pdf - $HOME/Desktop/nextmonth.pdf threw out /home/mwilson/bin/nextmonth: line 3: 08: value too great for base (error token is "08") `date +%m` returns '08' for August, which is an illegal octal number. The fix for this is to force decimal casting, the way Ada does: pcal -l -m -Pletter $((10#`date +%m` % 12 + 1)) $(date -d"next month" +%Y) | ps2pdf - $HOME/Desktop/nextmonth.pdf I guess `$(` takes special care of pound signs. So I've learned something again.