lib: Fix timeformat.parseShortDate()

Do the "strip off time and set to midnight" step already for the
reference Date input of parse(). Substracting it afterwards previously
caused the returned date to be off by one day for time zones East of
UTC.

Test with:

    for TZ in America/New_York UTC Europe/Berlin; do pytest -k timeformat || break; done

pkg/base1/test-timeformat.ts

@@ -124,21 +124,24 @@ QUnit.test("firstDayOfWeek", assert => {
  assert.equal(timeformat.firstDayOfWeek(), 1);
 });
 
-// FIXME: This test is currently time zone dependent; parseShortDate() always
-// interprets its argument as midnight UTC instead of local time; so it's even
-// off by a day for any TZ east of UTC.
-QUnit.skip("parsing", assert => {
+QUnit.test("parsing", assert => {
  cockpit.language = "en";
  const en = timeformat.parseShortDate("1/20/2024");
- assert.equal(en.toISOString(), "2024-01-20T00:00:00.000Z");
+ assert.equal(en.getDate(), 20);
+ assert.equal(en.getMonth(), 0); // yes, starting from 0
+ assert.equal(en.getFullYear(), "2024");
 
  cockpit.language = "en_GB";
  const engb = timeformat.parseShortDate("20/01/2024");
- assert.equal(engb.toISOString(), "2024-01-20T00:00:00.000Z");
+ assert.equal(engb.getDate(), 20);
+ assert.equal(engb.getMonth(), 0); // yes, starting from 0
+ assert.equal(engb.getFullYear(), "2024");
 
  cockpit.language = "de";
  const de = timeformat.parseShortDate("20.01.2024");
- assert.equal(de.toISOString(), "2024-01-20T00:00:00.000Z");
+ assert.equal(de.getDate(), 20);
+ assert.equal(de.getMonth(), 0); // yes, starting from 0
+ assert.equal(de.getFullYear(), "2024");
 });
 
 QUnit.start();

pkg/lib/timeformat.ts

@@ -50,12 +50,10 @@ export const distanceToNow = (t: Time, addSuffix?: boolean): string => formatDis
 
 // Parse a string localized date like 30.06.21 to a Date Object
 export function parseShortDate(dateStr: string): Date {
- const parsed = parse(dateStr, dateShortFormat(), new Date());
-
- // Strip time which may cause bugs in calendar
- const time = parsed.getTime();
- const timePortion = time % (3600 * 1000 * 24);
- return new Date(time - timePortion);
+ // strip off time (i.e. set to midnight), to avoid confusing calendar widgets
+ const now = new Date();
+ const today = new Date(now.getFullYear(), now.getMonth(), now.getDate());
+ return parse(dateStr, dateShortFormat(), today);
 }
 
 /***