deps: icu 63.1 bump (CLDR 34)

- Full release notes: http://site.icu-project.org/download/63

Fixes: https://github.com/nodejs/node/issues/22344

PR-URL: https://github.com/nodejs/node/pull/23715
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/deps/icu-small/source/i18n/unicode/ucal.h b/deps/icu-small/source/i18n/unicode/ucal.h
index 10d8bc5274..889a1ec51d 100644
--- a/deps/icu-small/source/i18n/unicode/ucal.h
+++ b/deps/icu-small/source/i18n/unicode/ucal.h
@@ -139,6 +139,19 @@
  * For example, subtracting 5 days from the date <code>September 12, 1996</code>
  * results in <code>September 7, 1996</code>.
  *
+ * <p>
+ * The Japanese calendar uses a combination of era name and year number.
+ * When an emperor of Japan abdicates and a new emperor ascends the throne,
+ * a new era is declared and year number is reset to 1. Even if the date of
+ * abdication is scheduled ahead of time, the new era name might not be
+ * announced until just before the date. In such case, ICU4C may include
+ * a start date of future era without actual era name, but not enabled
+ * by default. ICU4C users who want to test the behavior of the future era
+ * can enable the tentative era by:
+ * <ul>
+ * <li>Environment variable <code>ICU_ENABLE_TENTATIVE_ERA=true</code>.</li>
+ * </ul>
+ *
  * @stable ICU 2.0
  */