diff --git a/packages/jest-types/src/Config.ts b/packages/jest-types/src/Config.ts
index 3287a3733bc6..0e64e304fd52 100644
--- a/packages/jest-types/src/Config.ts
+++ b/packages/jest-types/src/Config.ts
@@ -58,7 +58,7 @@ export type FakeTimersConfig = {
    */
   doNotFake?: Array<FakeableAPI>;
   /**
-   * Sets current system time to be used by fake timers.
+   * Sets current system time to be used by fake timers, in milliseconds.
    *
    * @defaultValue
    * The default is `Date.now()`.