src/java.base/share/classes/java/time/format/DateTimeFormatterBuilder.java

@@ -829,10 +829,14 @@
      * The {@linkplain ResolverStyle resolver style} has no effect on instant parsing.
      * The end-of-day time of '24:00' is handled as midnight at the start of the following day.
      * The leap-second time of '23:59:59' is handled to some degree, see
      * {@link DateTimeFormatter#parsedLeapSecond()} for full details.
      * <p>
+     * When formatting, the instant will always be suffixed by 'Z' to indicate UTC.
+     * When parsing, the behaviour of {@code appendOffsetId()} will be used to parse the offset,
+     * converting the instant to UTC as necessary.</p>
+     * <p>
      * An alternative to this method is to format/parse the instant as a single
      * epoch-seconds value. That is achieved using {@code appendValue(INSTANT_SECONDS)}.
      *
      * @return this, for chaining, not null
      */

@@ -3460,11 +3464,11 @@
                     .append(DateTimeFormatter.ISO_LOCAL_DATE).appendLiteral('T')
                     .appendValue(HOUR_OF_DAY, 2).appendLiteral(':')
                     .appendValue(MINUTE_OF_HOUR, 2).appendLiteral(':')
                     .appendValue(SECOND_OF_MINUTE, 2)
                     .appendFraction(NANO_OF_SECOND, minDigits, maxDigits, true)
-                    .appendLiteral('Z')
+                    .appendOffsetId()
                     .toFormatter().toPrinterParser(false);
             DateTimeParseContext newContext = context.copy();
             int pos = parser.parse(newContext, text, position);
             if (pos < 0) {
                 return pos;

@@ -3478,10 +3482,11 @@
             int min = newContext.getParsed(MINUTE_OF_HOUR).intValue();
             Long secVal = newContext.getParsed(SECOND_OF_MINUTE);
             Long nanoVal = newContext.getParsed(NANO_OF_SECOND);
             int sec = (secVal != null ? secVal.intValue() : 0);
             int nano = (nanoVal != null ? nanoVal.intValue() : 0);
+            int offset = newContext.getParsed(OFFSET_SECONDS).intValue();
             int days = 0;
             if (hour == 24 && min == 0 && sec == 0 && nano == 0) {
                 hour = 0;
                 days = 1;
             } else if (hour == 23 && min == 59 && sec == 60) {

@@ -3490,11 +3495,11 @@
             }
             int year = (int) yearParsed % 10_000;
             long instantSecs;
             try {
                 LocalDateTime ldt = LocalDateTime.of(year, month, day, hour, min, sec, 0).plusDays(days);
-                instantSecs = ldt.toEpochSecond(ZoneOffset.UTC);
+                instantSecs = ldt.toEpochSecond(ZoneOffset.ofTotalSeconds(offset));
                 instantSecs += Math.multiplyExact(yearParsed / 10_000L, SECONDS_PER_10000_YEARS);
             } catch (RuntimeException ex) {
                 return ~position;
             }
             int successPos = pos;