Data Limitations

What the records here do not cover, and why

NBA

Games from 1947 to 2001 come from FiveThirtyEight's results, which mark a playoff game and name no round. Each season's Finals are found from the games after loading; the earlier rounds are not named.
ABA games are not counted. The NBA's record books count the Pacers, Nuggets, Spurs and Nets from 1977, and so does this.
From 2002 games come from sportsdataverse (ESPN's records). 2002 and 2003 name no playoff round either.
The names of the fifteen defunct BAA and NBA clubs come from Wikipedia.
No head coaches are on record yet, so there is no coaches page.

The season being played is shown from ESPN's public scoreboard, which can briefly differ from the league's own record of a game.
No box scores or player statistics are loaded. Records that need them — no-hitters, cycles, earned run averages, a player's game — are left out rather than shown empty, and there are no player pages.
Each league's day-by-day and week-by-week scores come from ESPN's scoreboard, which reaches back years rather than to each league's first season. "Every season, from the record" under that list has the whole history.