fix local time

package.json

@@ -29,7 +29,7 @@
   "scripts": {
     "test": "yarn test:mocha && yarn test:tsc && yarn test:lint && yarn test:prettier",
     "test:coverage": "npx c8 yarn test:mocha",
-    "test:mocha": "mkdir -p test/output && mocha 'test/**/*-test.*' 'test/plot.js'",
+    "test:mocha": "mkdir -p test/output && TZ=America/Los_Angeles mocha 'test/**/*-test.*' 'test/plot.js'",
     "test:lint": "eslint src test",
     "test:prettier": "prettier --check src test",
     "test:tsc": "tsc",

src/marks/axis.js

@@ -638,7 +638,7 @@ export function inferTickFormat(scale, data, ticks, tickFormat, anchor) {
   return typeof tickFormat === "function"
     ? tickFormat
     : tickFormat === undefined && data && isTemporal(data)
-    ? inferTimeFormat(data, anchor) ?? formatDefault
+    ? inferTimeFormat(scale.type, data, anchor) ?? formatDefault
     : scale.tickFormat
     ? scale.tickFormat(typeof ticks === "number" ? ticks : null, tickFormat)
     : tickFormat === undefined

src/time.js

@@ -123,23 +123,39 @@ for (const [name, interval] of utcIntervals) {
   interval[intervalType] = "utc";
 }
 
+const utcFormatIntervals = [
+  ["year", utcYear, "utc"],
+  ["month", utcMonth, "utc"],
+  ["day", unixDay, "utc", 6 * durationMonth],
+  ["hour", utcHour, "utc", 3 * durationDay],
+  ["minute", utcMinute, "utc", 6 * durationHour],
+  ["second", utcSecond, "utc", 30 * durationMinute]
+];
+
+const timeFormatIntervals = [
+  ["year", timeYear, "time"],
+  ["month", timeMonth, "time"],
+  ["day", timeDay, "time", 6 * durationMonth],
+  ["hour", timeHour, "time", 3 * durationDay],
+  ["minute", timeMinute, "time", 6 * durationHour],
+  ["second", timeSecond, "time", 30 * durationMinute]
+];
+
 // An interleaved array of UTC and local time intervals, in descending order
 // from largest to smallest, used to determine the most specific standard time
 // format for a given array of dates. This is a subset of the tick intervals
 // listed above; we only need the breakpoints where the format changes.
 const formatIntervals = [
-  ["year", utcYear, "utc"],
-  ["year", timeYear, "time"],
-  ["month", utcMonth, "utc"],
-  ["month", timeMonth, "time"],
-  ["day", unixDay, "utc", 6 * durationMonth],
-  ["day", timeDay, "time", 6 * durationMonth],
+  utcFormatIntervals[0],
+  timeFormatIntervals[0],
+  utcFormatIntervals[1],
+  timeFormatIntervals[1],
+  utcFormatIntervals[2],
+  timeFormatIntervals[2],
   // Below day, local time typically has an hourly offset from UTC and hence the
   // two are aligned and indistinguishable; therefore, we only consider UTC, and
   // we don’t consider these if the domain only has a single value.
-  ["hour", utcHour, "utc", 3 * durationDay],
-  ["minute", utcMinute, "utc", 6 * durationHour],
-  ["second", utcSecond, "utc", 30 * durationMinute]
+  ...utcFormatIntervals.slice(3)
 ];
 
 function parseInterval(input, intervals, type) {
@@ -238,16 +254,20 @@ function getTimeTemplate(anchor) {
     : (f1, f2) => `${f1}\n${f2}`;
 }
 
+function getFormatIntervals(type) {
+  return type === "time" ? timeFormatIntervals : type === "utc" ? utcFormatIntervals : formatIntervals;
+}
+
 // Given an array of dates, returns the largest compatible standard time
 // interval. If no standard interval is compatible (other than milliseconds,
 // which is universally compatible), returns undefined.
-export function inferTimeFormat(dates, anchor) {
+export function inferTimeFormat(type, dates, anchor) {
   const step = max(pairs(dates, (a, b) => Math.abs(b - a))); // maybe undefined!
   if (step < 1000) return formatTimeInterval("millisecond", "utc", anchor);
-  for (const [name, interval, type, maxStep] of formatIntervals) {
+  for (const [name, interval, intervalType, maxStep] of getFormatIntervals(type)) {
     if (step > maxStep) break; // e.g., 52 weeks
     if (name === "hour" && !step) break; // e.g., domain with a single date
-    if (dates.every((d) => interval.floor(d) >= d)) return formatTimeInterval(name, type, anchor);
+    if (dates.every((d) => interval.floor(d) >= d)) return formatTimeInterval(name, intervalType, anchor);
   }
 }
 

test/plots/time-axis.ts

@@ -148,3 +148,14 @@ export async function warnTimeAxisOrdinalExplicitIncompatibleTicks() {
     marks: [Plot.barY(aapl, Plot.groupX({y: "median", title: "min"}, {title: "Date", x: "Date", y: "Close"}))]
   });
 }
+
+export async function timeAxisLocal() {
+  const dates = [
+    "2023-09-30T15:05:48.452Z",
+    "2023-09-30T16:05:48.452Z",
+    "2023-09-30T17:05:48.452Z",
+    "2023-09-30T18:05:48.452Z",
+    "2023-09-30T19:05:48.452Z"
+  ].map((d) => new Date(d));
+  return Plot.dotX(dates).plot({x: {type: "time"}});
+}