diff --git a/ui/litellm-dashboard/src/app/(dashboard)/guardrails-monitor/_components/GuardrailDetail.integration.test.tsx b/ui/litellm-dashboard/src/app/(dashboard)/guardrails-monitor/_components/GuardrailDetail.integration.test.tsx
index 6bbdf299c64..32f2998ee7e 100644
--- a/ui/litellm-dashboard/src/app/(dashboard)/guardrails-monitor/_components/GuardrailDetail.integration.test.tsx
+++ b/ui/litellm-dashboard/src/app/(dashboard)/guardrails-monitor/_components/GuardrailDetail.integration.test.tsx
@@ -51,8 +51,8 @@ describe("GuardrailDetail sends the viewer's local day as instants", () => {
     const params = usageLogsQuery();
 
     // 00:00 and 23:59:59 on 2026-08-10 in IST, expressed as instants.
-    expect(params?.get("start_date")).toBe("2026-08-09T18:30:00Z");
-    expect(params?.get("end_date")).toBe("2026-08-10T18:29:59Z");
+    expect(params?.get("start_date")).toBe("2026-08-09T18:30:00.000Z");
+    expect(params?.get("end_date")).toBe("2026-08-10T18:29:59.999Z");
   });
 
   it("never sends a bare calendar date, which the endpoint would read as UTC", async () => {
diff --git a/ui/litellm-dashboard/src/components/GuardrailsMonitor/guardrailLogsWindow.test.ts b/ui/litellm-dashboard/src/components/GuardrailsMonitor/guardrailLogsWindow.test.ts
index 433e74e2817..c86c903dd57 100644
--- a/ui/litellm-dashboard/src/components/GuardrailsMonitor/guardrailLogsWindow.test.ts
+++ b/ui/litellm-dashboard/src/components/GuardrailsMonitor/guardrailLogsWindow.test.ts
@@ -20,8 +20,8 @@ describe("toUtcInstantRange, east of UTC (Asia/Kolkata, +05:30)", () => {
 
   it("resolves the local day to instants rather than the UTC day", () => {
     expect(toUtcInstantRange("2026-08-10", "2026-08-10")).toEqual({
-      start: "2026-08-09T18:30:00Z",
-      end: "2026-08-10T18:29:59Z",
+      start: "2026-08-09T18:30:00.000Z",
+      end: "2026-08-10T18:29:59.999Z",
     });
   });
 
@@ -46,10 +46,16 @@ describe("toUtcInstantRange, east of UTC (Asia/Kolkata, +05:30)", () => {
     expect(Date.parse(end)).toBeGreaterThan(Date.parse("2026-08-10T12:00:00Z"));
   });
 
+  it("keeps a row in the final millisecond of the local day", () => {
+    const { end } = toUtcInstantRange("2026-08-10", "2026-08-10");
+    // 23:59:59.500 local. Truncating the inclusive bound to whole seconds drops it.
+    expect(Date.parse(end)).toBeGreaterThanOrEqual(Date.parse("2026-08-10T18:29:59.500Z"));
+  });
+
   it("spans a multi-day range end to end", () => {
     expect(toUtcInstantRange("2026-08-03", "2026-08-10")).toEqual({
-      start: "2026-08-02T18:30:00Z",
-      end: "2026-08-10T18:29:59Z",
+      start: "2026-08-02T18:30:00.000Z",
+      end: "2026-08-10T18:29:59.999Z",
     });
   });
 });
@@ -59,8 +65,8 @@ describe("toUtcInstantRange, west of UTC (America/Los_Angeles, -07:00 in August)
 
   it("resolves the local day to instants rather than the UTC day", () => {
     expect(toUtcInstantRange("2026-08-10", "2026-08-10")).toEqual({
-      start: "2026-08-10T07:00:00Z",
-      end: "2026-08-11T06:59:59Z",
+      start: "2026-08-10T07:00:00.000Z",
+      end: "2026-08-11T06:59:59.999Z",
     });
   });
 
@@ -80,8 +86,8 @@ describe("toUtcInstantRange, on UTC", () => {
 
   it("matches the day the endpoint would have assumed", () => {
     expect(toUtcInstantRange("2026-08-10", "2026-08-10")).toEqual({
-      start: "2026-08-10T00:00:00Z",
-      end: "2026-08-10T23:59:59Z",
+      start: "2026-08-10T00:00:00.000Z",
+      end: "2026-08-10T23:59:59.999Z",
     });
   });
 });
diff --git a/ui/litellm-dashboard/src/components/GuardrailsMonitor/guardrailLogsWindow.ts b/ui/litellm-dashboard/src/components/GuardrailsMonitor/guardrailLogsWindow.ts
index b519b268f83..f75edf44c26 100644
--- a/ui/litellm-dashboard/src/components/GuardrailsMonitor/guardrailLogsWindow.ts
+++ b/ui/litellm-dashboard/src/components/GuardrailsMonitor/guardrailLogsWindow.ts
@@ -5,14 +5,14 @@ export interface UtcInstantRange {
   end: string;
 }
 
+const UTC_INSTANT = "YYYY-MM-DDTHH:mm:ss.SSS[Z]";
+
 /**
- * `/guardrails/usage/logs` filters `start_time`, a real timestamp column, but pads a
- * bare `YYYY-MM-DD` out to `T00:00:00+00:00` / `T23:59:59+00:00`. Sending the picker's
- * local calendar date therefore shifts the window by the viewer's UTC offset. Resolving
- * the local day here and sending instants keeps the bound exact; the endpoint already
- * parses a value carrying a `T`.
+ * `/guardrails/usage/logs` pads a bare `YYYY-MM-DD` to a whole UTC day, so the picker's
+ * local date lands the viewer's offset away from the range they chose. Milliseconds are
+ * kept because the inclusive end bound otherwise drops the final 999ms of that day.
  */
 export const toUtcInstantRange = (startDate: string, endDate: string): UtcInstantRange => ({
-  start: moment(startDate).startOf("day").utc().format(),
-  end: moment(endDate).endOf("day").utc().format(),
+  start: moment(startDate).startOf("day").utc().format(UTC_INSTANT),
+  end: moment(endDate).endOf("day").utc().format(UTC_INSTANT),
 });