add constants for millisecond amounts

Signed-off-by: nkomonen-amazon <[email protected]>

packages/core/src/shared/datetime.ts

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+/*!
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+// constants for working with milliseconds
+export const oneSecond = 1000
+export const oneMinute = oneSecond * 60
+export const oneHour = oneMinute * 60
+export const oneDay = oneHour * 24

packages/core/src/test/shared/datetime.test.ts

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+/*!
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import assert from 'assert'
+import { oneSecond, oneMinute, oneHour, oneDay } from '../../shared/datetime'
+
+// Test that the following imports all equal the expected milliseconds
+describe('millisecond constants', () => {
+    it('has expected milliseconds', () => {
+        assert.strictEqual(oneSecond, 1000)
+        assert.strictEqual(oneMinute, 1000 * 60)
+        assert.strictEqual(oneHour, 1000 * 60 * 60)
+        assert.strictEqual(oneDay, 1000 * 60 * 60 * 24)
+    })
+})