via sigrun (emphasis mine):
If your Friends have posted more entries than appear on your Friends page, then you can follow links on the page to view their older entries. However, your Friends page will only display up to 1000 of the entries posted in the last two weeks. If you have a Paid Account, you may also view your Friends page from any day by appending the date to the Friends page URL in this format: http://[USERNAME].livejournal.com/friends/?date=YYYY-MM-DD, where YYYY-MM-DD is the date in the year-month-day format, eg. 2009-01-06 for January 6, 2009. Note that month and day must have 2 digits, even for January-September or the first 9 days of the month.