diff --git a/files/en-us/web/javascript/reference/global_objects/intl/supportedvaluesof/index.md b/files/en-us/web/javascript/reference/global_objects/intl/supportedvaluesof/index.md
index baef555193e9415..93d489190c1e247 100644
--- a/files/en-us/web/javascript/reference/global_objects/intl/supportedvaluesof/index.md
+++ b/files/en-us/web/javascript/reference/global_objects/intl/supportedvaluesof/index.md
@@ -72,7 +72,7 @@ Below are all values that are commonly supported by browsers for the `calendar`
 | `hebrew`           | Traditional Hebrew calendar                                                                                                                                                                                                                                                                                                                                      |
 | `indian`           | Indian calendar                                                                                                                                                                                                                                                                                                                                                  |
 | `islamic`          | Hijri calendar, unspecified algorithm. **Note:** As of April 2025, this is an astronomical simulation whose parameters are undocumented and that is not known to match a specific Hijri calendar variant from non-software contexts. For well-specified results, use one of the three specific variants: `islamic-umalqura`, `islamic-tbla`, or `islamic-civil`. |
-| `islamic-umalqura` | Hijri calendar, Umm al-Qura (uses KACST-calculated months from the start of 1300 AH to the end of 1600 AH and falls back to `islamic-civil` outside that range)                                                                                                                                                                                                  |
+| `islamic-umalqura` | Hijri calendar, Umm al-Qura (uses KACST-calculated months from the start of 1300 AH (1882-11-12 ISO) to the end of 1600 AH (2174-11-25 ISO) and falls back to `islamic-civil` outside that range)                                                                                                                                                                |
 | `islamic-tbla`     | Hijri calendar, tabular/rule-based with leap year rule II (leap years 2,5,7,10,13,16,18,21,24,26,29 in the 30-year cycle (1-based numbering)) and Thursday/astronomical epoch (July 15, 622 Julian / 0622-07-18 ISO)                                                                                                                                             |
 | `islamic-civil`    | Hijri calendar, tabular/rule-based with leap year rule II (leap years 2,5,7,10,13,16,18,21,24,26,29 in the 30-year cycle (1-based numbering)) and Friday/civil epoch (July 16, 622 Julian / 0622-07-19 ISO)                                                                                                                                                      |
 | `iso8601`          | ISO calendar (variant of the Gregorian calendar with week rules and formatting parameters made region-independent)                                                                                                                                                                                                                                               |