diff --git a/web/api/v1/api.go b/web/api/v1/api.go
index 0279f727f1..46666af90c 100644
--- a/web/api/v1/api.go
+++ b/web/api/v1/api.go
@@ -834,12 +834,22 @@ func (api *API) labelValues(r *http.Request) (result apiFuncResult) {
 }
 
 var (
-	// MinTime is the default timestamp used for the begin of optional time ranges.
-	// Exposed to let downstream projects to reference it.
+	// MinTime is the default timestamp used for the start of optional time ranges.
+	// Exposed to let downstream projects reference it.
+	//
+	// Historical note: This should just be time.Unix(math.MinInt64/1000, 0).UTC(),
+	// but it was set to a higher value in the past due to a misunderstanding.
+	// The value is still low enough for practical purposes, so we don't want
+	// to change it now, avoiding confusion for importers of this variable.
 	MinTime = time.Unix(math.MinInt64/1000+62135596801, 0).UTC()
 
 	// MaxTime is the default timestamp used for the end of optional time ranges.
 	// Exposed to let downstream projects to reference it.
+	//
+	// Historical note: This should just be time.Unix(math.MaxInt64/1000, 0).UTC(),
+	// but it was set to a lower value in the past due to a misunderstanding.
+	// The value is still high enough for practical purposes, so we don't want
+	// to change it now, avoiding confusion for importers of this variable.
 	MaxTime = time.Unix(math.MaxInt64/1000-62135596801, 999999999).UTC()
 
 	minTimeFormatted = MinTime.Format(time.RFC3339Nano)