Stories depicting such events as weddings, births, and other important milestones frequently stretched over two-, three-, and four-part episodes.
The theme song for One Day at a Time, "This is It", was composed by Brill Building songwriter Jeff Barry and his wife Nancy Barry, and performed by recording artist Polly Cutter.
Julie and Barbara advance through high school and into the working world, and Julie eventually marries flight attendant Max Horvath.
Alex, the orphaned son of Ann's deceased boyfriend, moves in, changing the dynamics in the female-dominated apartment.
From 1982 to 1984, the series was taped at Universal Studios.
Like many sitcoms developed by Norman Lear, One Day at a Time often tackled serious issues in life and relationships, particularly those related to second-wave feminism.
The series was created by Whitney Blake and Allan Manings, a husband-and-wife writing duo who were both actors in the 1950s and 1960s.
They become engaged and call it off on their wedding day, when David says he wants kids, but Ann does not.
Dwayne Schneider, the building's quirky superintendent (most often referred to only by his last name), provides usually unwanted advice to the tenants.
Actors Bonnie Franklin, Pat Harrington, Jr., and Valerie Bertinelli were the only cast members to remain with the series throughout its entire run.
Lead actress Mackenzie Phillips was fired after the fifth season due to growing problems with substance abuse. Original cast member Richard Masur was written out early in the second season, but returned as a guest star in the sixth-season finale.
After David takes a job in Los Angeles, the focus squarely rests on Ann's dilemmas as a single mother and career woman, as well as the girls' growing pains, with Schneider becoming a more welcomed part of the family.