Add timestamp utilities with helpful names

ts/test-both/util/timestamp_test.ts

@@ -0,0 +1,37 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { assert } from 'chai';
+
+import { isOlderThan, isMoreRecentThan } from '../../util/timestamp';
+
+const ONE_HOUR = 3600 * 1000;
+const ONE_DAY = 24 * ONE_HOUR;
+
+describe('timestamp', () => {
+  describe('isOlderThan', () => {
+    it('returns false on recent and future timestamps', () => {
+      assert.isFalse(isOlderThan(Date.now(), ONE_DAY));
+      assert.isFalse(isOlderThan(Date.now() + ONE_DAY, ONE_DAY));
+    });
+
+    it('returns true on old enough timestamps', () => {
+      assert.isFalse(isOlderThan(Date.now() - ONE_DAY + ONE_HOUR, ONE_DAY));
+      assert.isTrue(isOlderThan(Date.now() - ONE_DAY - ONE_HOUR, ONE_DAY));
+    });
+  });
+
+  describe('isMoreRecentThan', () => {
+    it('returns true on recent and future timestamps', () => {
+      assert.isTrue(isMoreRecentThan(Date.now(), ONE_DAY));
+      assert.isTrue(isMoreRecentThan(Date.now() + ONE_DAY, ONE_DAY));
+    });
+
+    it('returns false on old enough timestamps', () => {
+      assert.isTrue(isMoreRecentThan(Date.now() - ONE_DAY + ONE_HOUR, ONE_DAY));
+      assert.isFalse(
+        isMoreRecentThan(Date.now() - ONE_DAY - ONE_HOUR, ONE_DAY)
+      );
+    });
+  });
+});