diff --git a/app/lib/__tests__/utils.test.ts b/app/lib/__tests__/utils.test.ts
index 5c62db9b..0ff9153f 100644
--- a/app/lib/__tests__/utils.test.ts
+++ b/app/lib/__tests__/utils.test.ts
@@ -1,5 +1,12 @@
 import { getFiltersFromSearchParams } from "../utils";
-import { describe, test, expect } from "vitest";
+import { describe, test, expect, beforeEach, afterEach, vi } from "vitest";
+import { getDateTimeRange } from "../utils";
+import dayjs from "dayjs";
+import utc from "dayjs/plugin/utc";
+import timezone from "dayjs/plugin/timezone";
+
+dayjs.extend(utc);
+dayjs.extend(timezone);
 
 // test this getfiltersfromsearchparams function
 describe("getFiltersFromSearchParams", () => {
@@ -24,3 +31,63 @@ describe("getFiltersFromSearchParams", () => {
         });
     });
 });
+
+describe("getDateTimeRange", () => {
+    const tz = "America/Los_Angeles";
+    const mockDate = new Date("2024-01-15T15:00:00Z"); // 7am PST on Jan 15, 2024
+
+    beforeEach(() => {
+        vi.setSystemTime(mockDate);
+    });
+
+    afterEach(() => {
+        vi.restoreAllMocks();
+    });
+
+    test("handles 'today' interval", () => {
+        const { startDate, endDate } = getDateTimeRange("today", tz);
+
+        // Start date should be Jan 15, 2024 00:00 PST
+        expect(startDate).toEqual(new Date("2024-01-15T08:00:00Z")); // 00:00 PST = 08:00 UTC
+        expect(endDate).toEqual(new Date("2024-01-15T15:00:00Z")); // Current time (7am PST = 15:00 UTC)
+    });
+
+    test("handles 'yesterday' interval", () => {
+        const { startDate, endDate } = getDateTimeRange("yesterday", tz);
+
+        expect(startDate).toEqual(new Date("2024-01-14T08:00:00Z"));
+        expect(endDate).toEqual(new Date("2024-01-15T08:00:00.001Z"));
+    });
+
+    test("handles '7d' interval", () => {
+        const { startDate, endDate } = getDateTimeRange("7d", tz);
+
+        expect(startDate).toEqual(new Date("2024-01-08T08:00:00Z"));
+        expect(endDate).toEqual(new Date("2024-01-15T15:00:00Z"));
+    });
+
+    test("handles '1d' interval", () => {
+        const { startDate, endDate } = getDateTimeRange("1d", tz);
+
+        expect(startDate).toEqual(new Date("2024-01-14T15:00:00Z"));
+        expect(endDate).toEqual(new Date("2024-01-15T15:00:00Z"));
+    });
+
+    test("works with different timezones", () => {
+        const tokyoTz = "Asia/Tokyo"; // UTC+9
+        const londonTz = "Europe/London"; // UTC+0 in January
+
+        // When it's 7am PST (15:00 UTC) on Jan 15:
+        // - Tokyo: 00:00 JST on Jan 16
+        // - London: 15:00 GMT on Jan 15
+        // - LA: 7:00 PST on Jan 15
+
+        const tokyo = getDateTimeRange("today", tokyoTz);
+        const london = getDateTimeRange("today", londonTz);
+
+        // Tokyo's start date should be Jan 15 15:00 UTC (00:00 JST Jan 16)
+        expect(tokyo.startDate).toEqual(new Date("2024-01-15T15:00:00Z"));
+        // London's start date should be Jan 15 00:00 UTC
+        expect(london.startDate).toEqual(new Date("2024-01-15T00:00:00Z"));
+    });
+});