How do I do date math in a bash script on OS X Leopard?

Question

I realize I could whip up a little C or Ruby program to do this, but I want my script to have as few dependencies as possible.

Given that caveat, how does one d

Answer 1

Because MacOS is based on BSD, not linux, the command is actually:

date -v-1d

The adjust switch takes the format -v[+/-](number)[ymwdHMS].