how to get calendar- for an offset day

[Mirko]

Hi,

For a personal log, I use the `calendar-current-date' function
together with calendar-date-display-form to insert the current date
into the diary.  But sometimes I am lazy, or I forget, and I need to
insert yesterday's date into the calendar.

I did not find anything in calendar.el (but I might have missed it).
Any other options?

Thanks,

Mirko