Let's call your date field something original like "DateField".
Then a script like
Set Variable [$Date,DateField]
Enter Find Mode
Set Field [DateField,$Date-1]
Will find all records dated one day earlier than the date stored in DateField.
A very useful concept to keep in mind is that date fields are really number fields with special built in formatting that displays the number of days from 0/0/0000 in a date format we humans can read. Since it is really a number, you can usually treat it like one in expressions and scripts.
How would you search for the previous day in a script?
if you want to find all record of yesterday:
Enter Find Mode [ ]
Set Field [ yourDateField ; Get ( CurrentDate ) - 1 ]
Perform Find [ ]