Tennis publishes match durations as though the quantity were obvious. It is not, and the figure a tournament prints depends on which of several clocks it consulted.
Playing time excludes the pauses
The strictest definition counts only time when the ball is in play or between points within a game, excluding changeovers, set breaks, medical timeouts and rain delays.
This is the figure closest to physical load, and it is what performance staff care about. It is also the hardest to produce, since it requires the pauses to be logged separately.
Few published durations use it, because the underlying breakdown is not usually available outside the tournament's own operation.
Court time is what the schedule uses
Tournament scheduling works from the interval between players walking on and walking off, which includes the warm-up and every stoppage.
This is the number that determines whether the next match starts on time, so it is the one operations staff track and the one the schedule is built from.
It is a poor measure of anything about the match itself, since a long rain delay inflates it without a ball being struck.
First serve to last point is the published figure
Most reported durations run from the first serve to the final point, including changeovers and interruptions but excluding warm-up.
It is a compromise: reproducible from the umpire's record, and roughly meaningful as a description of how long the contest lasted.
Records for the longest matches almost always use this definition, which is worth knowing before comparing two figures from different sources.
Why suspensions break every convention
A match suspended overnight and resumed the next day has to be handled explicitly. Counting the intervening hours would be absurd, so they are excluded.
Rain delays within a day are treated inconsistently. Some records subtract them and some do not, which is a large discrepancy on a long match.
Roofed venues have reduced the frequency of this problem without resolving the convention, so the ambiguity persists wherever weather still intervenes.
What the confusion costs
Longest-match claims are frequently comparing figures produced under different rules, which is why they are argued about more than the underlying facts warrant.
Workload analysis suffers more seriously. A player's accumulated court time across a tournament is a meaningful quantity only if the same definition applied throughout.
The fix is unglamorous: publish the definition next to the number. Almost nowhere in the sport is that done.

