Is there a way to search records by modified BEFORE?

Is there a way to search records by modified BEFORE?

I've looked in the API documentation and believe the following are true:

1. I can use the getRecords with LastModifiedTime to get all the records SINCE a time/date.

2. I cannot use the getSearchRecords using searchCondition=(LastModifiedTime|<|2012-08-29%2011:09:23)

For example: getSearchRecords& authtoken=XXXXXX&scope=crmapi&newFormat=1

&selectColumns=Leads(Lead Name,Company,Email,Mobile,Website)&searchCondition=(LastModifiedTime|<|2012-08-29%2011:09:23)" ;

For getSearchRecords I've also tried "modified", "modified time", "last modified" and anything else I could think of. I always get Error code 4832 (invalid parameter value)

Does anyone else know of another way that I might be able to fetch records that haven't been modified for 90 days?