was only the Pac-8. The conference had a round-robin of 14 games over 7 weekends. UCLA typically had 2 weekends with OOC games in mid-late January (perhaps a relic from when more schools had final exams in late January, which ND did until 1970 or so). UCLA usually came to the Midwest on one of those two weekends, playing in a doubleheader in Chicago Stadium until the mid-1970s, and playing at ND every January from 1971 through 1979 (which was the first year of the Pac-10). I believe in both 1971 and 1972, UCLA and ND both played at Chicago Stadium on Friday night (UCLA-Loyola, ND-Illinois), and then played each other at ND on Saturday in the late afternoon. In 1973 and 1974, the Chicago Stadium doubleheaders were the Thursday before UCLA visited ND, but ND didn't play at Chicago Stadium in 1974 (the year ND broke UCLA's 88-game winning streak).
During that period, ND almost always visited UCLA before the Bruins came to South Bend, either in December or early January (during Christmas break). The exception was the 1973-1974 season, when TVS convinced the schools to move the Pauley Pavilion game from December 22 to January 26 in a late-night slot (11:30 ET, 8:30 PT). That meant UCLA got a rematch with ND in Pauley just 7 days after ND had broken their 88-game winning streak. UCLA won that rematch in a blowout. ND got its first win at Pauley in December 1976, breaking an OOC home winning streak of over 100 games (and becoming the first OOC opponent ever to win at Pauley).
Things changed after the 1978-1979 season, UCLA's trips to ND moved around the calendar, usually coming in either December or February, with the only other January trip coming in 1986. ND played at UCLA in January a few times between 1980 and 1993, and in February in some other years. Most of those mid-season matchups came on weeks when UCLA played Southern Cal and no other conference opponent (as a result, most UCLA-USC games were played on Wednesday or Thursday nights).
With the increasing scheduling complications, the UCLA-ND rivalry went from twice annually (as it had been since Digger's first season in 1971-1972) to once per year (starting in 1983-1984). It ceased being an annual event after December 1995, which was ND's first season in the Big East.
In more recent years, there have been far fewer OOC games in January and February in general. When schools like ND and UCLA get "byes" during conference play, they used to schedule TV-friendly OOC games in those slots, but now they are far more likely to use those "byes" for much-needed rest.