diff --git a/.github/.release-please-manifest.json b/.github/.release-please-manifest.json
index 6f510540c..ef6e46afb 100644
--- a/.github/.release-please-manifest.json
+++ b/.github/.release-please-manifest.json
@@ -3,6 +3,7 @@
   "analyze": "1.0.0-alpha.7",
   "arcjet": "1.0.0-alpha.7",
   "arcjet-next": "1.0.0-alpha.7",
+  "duration": "1.0.0-alpha.7",
   "eslint-config": "1.0.0-alpha.7",
   "ip": "1.0.0-alpha.7",
   "logger": "1.0.0-alpha.7",
diff --git a/.github/release-please-config.json b/.github/release-please-config.json
index 7a0c88f1b..f4509ca3b 100644
--- a/.github/release-please-config.json
+++ b/.github/release-please-config.json
@@ -41,6 +41,10 @@
       "component": "@arcjet/next",
       "skip-github-release": true
     },
+    "duration": {
+      "component": "@arcjet/duration",
+      "skip-github-release": true
+    },
     "eslint-config": {
       "component": "@arcjet/eslint-config",
       "skip-github-release": true
@@ -79,6 +83,7 @@
         "@arcjet/analyze",
         "arcjet",
         "@arjcet/next",
+        "@arjcet/duration",
         "@arcjet/eslint-config",
         "@arcjet/ip",
         "@arcjet/logger",
diff --git a/README.md b/README.md
index 7e1f1dedc..e86257085 100644
--- a/README.md
+++ b/README.md
@@ -48,6 +48,8 @@ find a specific one through the categories and descriptions below.
   into the Arcjet protocol.
 - [`@arcjet/logger`](./logger/README.md): Logging interface which mirrors the
   console interface but allows log levels.
+- [`@arcjet/duration`](./duration/README.md): Utilities for parsing duration
+  strings into seconds integers.
 
 ### Internal development
 
diff --git a/arcjet/index.ts b/arcjet/index.ts
index 874f631bd..7aa8acafd 100644
--- a/arcjet/index.ts
+++ b/arcjet/index.ts
@@ -39,6 +39,7 @@ import {
   Timestamp,
 } from "@arcjet/protocol/proto.js";
 import * as analyze from "@arcjet/analyze";
+import * as duration from "@arcjet/duration";
 import { Logger } from "@arcjet/logger";
 
 export * from "@arcjet/protocol";
@@ -421,7 +422,7 @@ type TokenBucketRateLimitOptions = {
   match?: string;
   characteristics?: string[];
   refillRate: number;
-  interval: number;
+  interval: string | number;
   capacity: number;
 };
 
@@ -429,7 +430,7 @@ type FixedWindowRateLimitOptions = {
   mode?: ArcjetMode;
   match?: string;
   characteristics?: string[];
-  window: string;
+  window: string | number;
   max: number;
 };
 
@@ -437,7 +438,7 @@ type SlidingWindowRateLimitOptions = {
   mode?: ArcjetMode;
   match?: string;
   characteristics?: string[];
-  interval: number;
+  interval: string | number;
   max: number;
 };
 
@@ -605,7 +606,7 @@ export function tokenBucket(
     const characteristics = opt.characteristics;
 
     const refillRate = opt.refillRate;
-    const interval = opt.interval;
+    const interval = duration.parse(opt.interval);
     const capacity = opt.capacity;
 
     rules.push({
@@ -640,7 +641,7 @@ export function fixedWindow(
     const characteristics = opt.characteristics;
 
     const max = opt.max;
-    const window = opt.window;
+    const window = duration.parse(opt.window);
 
     rules.push({
       type: "RATE_LIMIT",
@@ -684,7 +685,7 @@ export function slidingWindow(
     const characteristics = opt.characteristics;
 
     const max = opt.max;
-    const interval = opt.interval;
+    const interval = duration.parse(opt.interval);
 
     rules.push({
       type: "RATE_LIMIT",
diff --git a/arcjet/package.json b/arcjet/package.json
index fb86f8696..c8f0d5ebd 100644
--- a/arcjet/package.json
+++ b/arcjet/package.json
@@ -32,6 +32,7 @@
   },
   "dependencies": {
     "@arcjet/analyze": "1.0.0-alpha.7",
+    "@arcjet/duration": "1.0.0-alpha.7",
     "@arcjet/logger": "1.0.0-alpha.7",
     "@arcjet/protocol": "1.0.0-alpha.7"
   },
diff --git a/arcjet/test/index.node.test.ts b/arcjet/test/index.node.test.ts
index 904d6cb3a..1888057cf 100644
--- a/arcjet/test/index.node.test.ts
+++ b/arcjet/test/index.node.test.ts
@@ -1948,6 +1948,36 @@ describe("Primitive > tokenBucket", () => {
     expect(rule).toHaveProperty("mode", "LIVE");
   });
 
+  test("can specify interval as a string duration", async () => {
+    const options = {
+      refillRate: 60,
+      interval: "60s",
+      capacity: 120,
+    };
+
+    const rules = tokenBucket(options);
+    expect(rules).toHaveLength(1);
+    expect(rules[0].type).toEqual("RATE_LIMIT");
+    expect(rules[0]).toHaveProperty("refillRate", 60);
+    expect(rules[0]).toHaveProperty("interval", 60);
+    expect(rules[0]).toHaveProperty("capacity", 120);
+  });
+
+  test("can specify interval as an integer duration", async () => {
+    const options = {
+      refillRate: 60,
+      interval: 60,
+      capacity: 120,
+    };
+
+    const rules = tokenBucket(options);
+    expect(rules).toHaveLength(1);
+    expect(rules[0].type).toEqual("RATE_LIMIT");
+    expect(rules[0]).toHaveProperty("refillRate", 60);
+    expect(rules[0]).toHaveProperty("interval", 60);
+    expect(rules[0]).toHaveProperty("capacity", 120);
+  });
+
   test("produces a rules based on single `limit` specified", async () => {
     const options = {
       match: "/test",
@@ -2096,6 +2126,32 @@ describe("Primitive > fixedWindow", () => {
     expect(rule).toHaveProperty("mode", "LIVE");
   });
 
+  test("can specify window as a string duration", async () => {
+    const options = {
+      window: "60s",
+      max: 1,
+    };
+
+    const rules = fixedWindow(options);
+    expect(rules).toHaveLength(1);
+    expect(rules[0].type).toEqual("RATE_LIMIT");
+    expect(rules[0]).toHaveProperty("window", 60);
+    expect(rules[0]).toHaveProperty("max", 1);
+  });
+
+  test("can specify window as an integer duration", async () => {
+    const options = {
+      window: 60,
+      max: 1,
+    };
+
+    const rules = fixedWindow(options);
+    expect(rules).toHaveLength(1);
+    expect(rules[0].type).toEqual("RATE_LIMIT");
+    expect(rules[0]).toHaveProperty("window", 60);
+    expect(rules[0]).toHaveProperty("max", 1);
+  });
+
   test("produces a rules based on single `limit` specified", async () => {
     const options = {
       match: "/test",
@@ -2111,7 +2167,7 @@ describe("Primitive > fixedWindow", () => {
     expect(rules[0]).toHaveProperty("match", "/test");
     expect(rules[0]).toHaveProperty("characteristics", ["ip.src"]);
     expect(rules[0]).toHaveProperty("algorithm", "FIXED_WINDOW");
-    expect(rules[0]).toHaveProperty("window", "1h");
+    expect(rules[0]).toHaveProperty("window", 3600);
     expect(rules[0]).toHaveProperty("max", 1);
   });
 
@@ -2140,7 +2196,7 @@ describe("Primitive > fixedWindow", () => {
         match: "/test",
         characteristics: ["ip.src"],
         algorithm: "FIXED_WINDOW",
-        window: "1h",
+        window: 3600,
         max: 1,
       }),
       expect.objectContaining({
@@ -2149,7 +2205,7 @@ describe("Primitive > fixedWindow", () => {
         match: "/test-double",
         characteristics: ["ip.src"],
         algorithm: "FIXED_WINDOW",
-        window: "2h",
+        window: 7200,
         max: 2,
       }),
     ]);
@@ -2187,7 +2243,7 @@ describe("Primitive > fixedWindow", () => {
         match: undefined,
         characteristics: undefined,
         algorithm: "FIXED_WINDOW",
-        window: "1h",
+        window: 3600,
         max: 1,
       }),
       expect.objectContaining({
@@ -2196,7 +2252,7 @@ describe("Primitive > fixedWindow", () => {
         match: undefined,
         characteristics: undefined,
         algorithm: "FIXED_WINDOW",
-        window: "2h",
+        window: 7200,
         max: 2,
       }),
     ]);
@@ -2234,6 +2290,32 @@ describe("Primitive > slidingWindow", () => {
     expect(rule).toHaveProperty("mode", "LIVE");
   });
 
+  test("can specify interval as a string duration", async () => {
+    const options = {
+      interval: "60s",
+      max: 1,
+    };
+
+    const rules = slidingWindow(options);
+    expect(rules).toHaveLength(1);
+    expect(rules[0].type).toEqual("RATE_LIMIT");
+    expect(rules[0]).toHaveProperty("interval", 60);
+    expect(rules[0]).toHaveProperty("max", 1);
+  });
+
+  test("can specify interval as an integer duration", async () => {
+    const options = {
+      interval: 60,
+      max: 1,
+    };
+
+    const rules = slidingWindow(options);
+    expect(rules).toHaveLength(1);
+    expect(rules[0].type).toEqual("RATE_LIMIT");
+    expect(rules[0]).toHaveProperty("interval", 60);
+    expect(rules[0]).toHaveProperty("max", 1);
+  });
+
   test("produces a rules based on single `limit` specified", async () => {
     const options = {
       match: "/test",
@@ -2390,7 +2472,7 @@ describe("Primitive > rateLimit", () => {
     expect(rules[0]).toHaveProperty("match", "/test");
     expect(rules[0]).toHaveProperty("characteristics", ["ip.src"]);
     expect(rules[0]).toHaveProperty("algorithm", "FIXED_WINDOW");
-    expect(rules[0]).toHaveProperty("window", "1h");
+    expect(rules[0]).toHaveProperty("window", 3600);
     expect(rules[0]).toHaveProperty("max", 1);
   });
 
@@ -2419,7 +2501,7 @@ describe("Primitive > rateLimit", () => {
         match: "/test",
         characteristics: ["ip.src"],
         algorithm: "FIXED_WINDOW",
-        window: "1h",
+        window: 3600,
         max: 1,
       }),
       expect.objectContaining({
@@ -2428,7 +2510,7 @@ describe("Primitive > rateLimit", () => {
         match: "/test-double",
         characteristics: ["ip.src"],
         algorithm: "FIXED_WINDOW",
-        window: "2h",
+        window: 7200,
         max: 2,
       }),
     ]);
@@ -2466,7 +2548,7 @@ describe("Primitive > rateLimit", () => {
         match: undefined,
         characteristics: undefined,
         algorithm: "FIXED_WINDOW",
-        window: "1h",
+        window: 3600,
         max: 1,
       }),
       expect.objectContaining({
@@ -2475,7 +2557,7 @@ describe("Primitive > rateLimit", () => {
         match: undefined,
         characteristics: undefined,
         algorithm: "FIXED_WINDOW",
-        window: "2h",
+        window: 7200,
         max: 2,
       }),
     ]);
diff --git a/duration/.eslintignore b/duration/.eslintignore
new file mode 100644
index 000000000..9cfa2cae7
--- /dev/null
+++ b/duration/.eslintignore
@@ -0,0 +1,6 @@
+/.turbo/
+/coverage/
+/node_modules/
+*.d.ts
+*.js
+!*.config.js
diff --git a/duration/.eslintrc.cjs b/duration/.eslintrc.cjs
new file mode 100644
index 000000000..abe4cd7b4
--- /dev/null
+++ b/duration/.eslintrc.cjs
@@ -0,0 +1,4 @@
+module.exports = {
+  root: true,
+  extends: ["@arcjet/eslint-config"],
+};
diff --git a/duration/.gitignore b/duration/.gitignore
new file mode 100644
index 000000000..35b162da3
--- /dev/null
+++ b/duration/.gitignore
@@ -0,0 +1,135 @@
+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+lerna-debug.log*
+.pnpm-debug.log*
+
+# Diagnostic reports (https://nodejs.org/api/report.html)
+report.[0-9]*.[0-9]*.[0-9]*.[0-9]*.json
+
+# Runtime data
+pids
+*.pid
+*.seed
+*.pid.lock
+
+# Directory for instrumented libs generated by jscoverage/JSCover
+lib-cov
+
+# Coverage directory used by tools like istanbul
+coverage
+*.lcov
+
+# nyc test coverage
+.nyc_output
+
+# Grunt intermediate storage (https://gruntjs.com/creating-plugins#storing-task-files)
+.grunt
+
+# Bower dependency directory (https://bower.io/)
+bower_components
+
+# node-waf configuration
+.lock-wscript
+
+# Compiled binary addons (https://nodejs.org/api/addons.html)
+build/Release
+
+# Dependency directories
+node_modules/
+jspm_packages/
+
+# Snowpack dependency directory (https://snowpack.dev/)
+web_modules/
+
+# TypeScript cache
+*.tsbuildinfo
+
+# Optional npm cache directory
+.npm
+
+# Optional eslint cache
+.eslintcache
+
+# Optional stylelint cache
+.stylelintcache
+
+# Microbundle cache
+.rpt2_cache/
+.rts2_cache_cjs/
+.rts2_cache_es/
+.rts2_cache_umd/
+
+# Optional REPL history
+.node_repl_history
+
+# Output of 'npm pack'
+*.tgz
+
+# Yarn Integrity file
+.yarn-integrity
+
+# dotenv environment variable files
+.env
+.env.development.local
+.env.test.local
+.env.production.local
+.env.local
+
+# parcel-bundler cache (https://parceljs.org/)
+.cache
+.parcel-cache
+
+# Next.js build output
+.next
+out
+
+# Nuxt.js build / generate output
+.nuxt
+dist
+
+# Gatsby files
+.cache/
+# Comment in the public line in if your project uses Gatsby and not Next.js
+# https://nextjs.org/blog/next-9-1#public-directory-support
+# public
+
+# vuepress build output
+.vuepress/dist
+
+# vuepress v2.x temp and cache directory
+.temp
+.cache
+
+# Docusaurus cache and generated files
+.docusaurus
+
+# Serverless directories
+.serverless/
+
+# FuseBox cache
+.fusebox/
+
+# DynamoDB Local files
+.dynamodb/
+
+# TernJS port file
+.tern-port
+
+# Stores VSCode versions used for testing VSCode extensions
+.vscode-test
+
+# yarn v2
+.yarn/cache
+.yarn/unplugged
+.yarn/build-state.yml
+.yarn/install-state.gz
+.pnp.*
+
+# Generated files
+index.js
+index.d.ts
+test/*.js
diff --git a/duration/LICENSE b/duration/LICENSE
new file mode 100644
index 000000000..261eeb9e9
--- /dev/null
+++ b/duration/LICENSE
@@ -0,0 +1,201 @@
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
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diff --git a/duration/README.md b/duration/README.md
new file mode 100644
index 000000000..e65d4dbcc
--- /dev/null
+++ b/duration/README.md
@@ -0,0 +1,52 @@
+<a href="https://arcjet.com" target="_arcjet-home">
+  <picture>
+    <source media="(prefers-color-scheme: dark)" srcset="https://arcjet.com/arcjet-logo-dark-planet-arrival.svg">
+    <img src="https://arcjet.com/arcjet-logo-light-planet-arrival.svg" alt="Arcjet Logo" height="144" width="auto">
+  </picture>
+</a>
+
+# `@arcjet/ip`
+
+<p>
+  <picture>
+    <source media="(prefers-color-scheme: dark)" srcset="https://img.shields.io/npm/v/%40arcjet%2Fip?style=flat-square&label=%E2%9C%A6Aj&labelColor=000000&color=5C5866">
+    <img alt="npm badge" src="https://img.shields.io/npm/v/%40arcjet%2Fip?style=flat-square&label=%E2%9C%A6Aj&labelColor=ECE6F0&color=ECE6F0">
+  </picture>
+</p>
+
+[Arcjet][arcjet] utilities for parsing duration strings.
+
+## Installation
+
+```shell
+npm install -S @arcjet/duration
+```
+
+## Example
+
+```ts
+import { parse } from "@arcjet/duration";
+
+const seconds = parse("1h");
+console.log(seconds); // prints 3600
+```
+
+## Implementation
+
+The implementation of this library is based on the [ParseDuration][go-parser]
+function in the Go stdlib. Originally licensed BSD-3.0 with the license included
+in our source code.
+
+We've chosen the approach of porting this to TypeScript because our protocol
+operates exclusively on unsigned 32-bit integers representing seconds. However,
+we don't want to require our SDK users to manually calculate seconds. By
+providing this utility, our SDK can accept duration strings and numbers while
+normalizing the values for our protocol.
+
+## License
+
+Licensed under the [Apache License, Version 2.0][apache-license].
+
+[arcjet]: https://arcjet.com
+[go-parser]: https://github.com/golang/go/blob/c18ddc84e1ec6406b26f7e9d0e1ee3d1908d7c27/src/time/format.go#L1589-L1686
+[apache-license]: http://www.apache.org/licenses/LICENSE-2.0
diff --git a/duration/index.ts b/duration/index.ts
new file mode 100644
index 000000000..690744a13
--- /dev/null
+++ b/duration/index.ts
@@ -0,0 +1,168 @@
+// This Parser is a TypeScript implementation of similar code in the Go stdlib
+// with deviations made to support usage in the Arcjet SDK.
+//
+// Parser source:
+// https://github.com/golang/go/blob/c18ddc84e1ec6406b26f7e9d0e1ee3d1908d7c27/src/time/format.go#L1589-L1686
+//
+// Licensed: BSD 3-Clause "New" or "Revised" License
+// Copyright (c) 2009 The Go Authors. All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+const second = 1;
+const minute = 60 * second;
+const hour = 60 * minute;
+const day = 24 * hour;
+
+const maxUint32 = 4294967295;
+
+const units = new Map([
+  ["s", second],
+  ["m", minute],
+  ["h", hour],
+  ["d", day],
+]);
+
+const integers = ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9"];
+
+// leadingInt consumes the leading [0-9]* from s.
+function leadingInt(s: string): [number, string] {
+  let i = 0;
+  let x = 0;
+  for (; i < s.length; i++) {
+    const c = s[i];
+    if (!integers.includes(c)) {
+      break;
+    }
+    x = x * 10 + parseInt(c, 10);
+    if (x > maxUint32) {
+      // overflow
+      throw new Error("bad [0-9]*"); // never printed
+    }
+  }
+  return [x, s.slice(i)];
+}
+
+/**
+ * Parses a duration into a number representing seconds while ensuring the value
+ * fits within an unsigned 32-bit integer.
+ *
+ * If a JavaScript number is provided to the function, it is validated and
+ * returned verbatim.
+ *
+ * If a string is provided to the function, it must be in the form of digits
+ * followed by a unit. Supported units are `s` (seconds), `m` (minutes), `h`
+ * (hours), and `d` (days).
+ *
+ * @param s The value to parse into seconds.
+ * @returns A number representing seconds parsed from the provided duration.
+ *
+ * @example
+ * parse("1s") === 1
+ * parse("1m") === 60
+ * parse("1h") === 3600
+ * parse("1d") === 86400
+ */
+export function parse(s: string | number): number {
+  const original = s;
+
+  if (typeof s === "number") {
+    if (s > maxUint32) {
+      throw new Error(`invalid duration: ${original}`);
+    }
+
+    if (s < 0) {
+      throw new Error(`invalid duration: ${original}`);
+    }
+
+    if (!Number.isInteger(s)) {
+      throw new Error(`invalid duration: ${original}`);
+    }
+
+    return s;
+  }
+
+  if (typeof s !== "string") {
+    throw new Error("can only parse a duration string");
+  }
+
+  let d = 0;
+
+  // Special case: if all that is left is "0", this is zero.
+  if (s === "0") {
+    return 0;
+  }
+  if (s === "") {
+    throw new Error(`invalid duration: ${original}`);
+  }
+
+  while (s !== "") {
+    let v = 0;
+
+    // The next character must be [0-9]
+    if (!integers.includes(s[0])) {
+      throw new Error(`invalid duration: ${original}`);
+    }
+    // Consume [0-9]*
+    [v, s] = leadingInt(s);
+    // Error on decimal (\.[0-9]*)?
+    if (s !== "" && s[0] == ".") {
+      // TODO: We could support decimals that turn into non-decimal seconds—e.g.
+      // 1.5hours becomes 5400 seconds
+      throw new Error(`unsupported decimal duration: ${original}`);
+    }
+
+    // Consume unit.
+    let i = 0;
+    for (; i < s.length; i++) {
+      const c = s[i];
+      if (integers.includes(c)) {
+        break;
+      }
+    }
+    if (i == 0) {
+      throw new Error(`missing unit in duration: ${original}`);
+    }
+    const u = s.slice(0, i);
+    s = s.slice(i);
+    const unit = units.get(u);
+    if (typeof unit === "undefined") {
+      throw new Error(`unknown unit "${u}" in duration ${original}`);
+    }
+    if (v > maxUint32 / unit) {
+      // overflow
+      throw new Error(`invalid duration ${original}`);
+    }
+    v *= unit;
+    d += v;
+    if (d > maxUint32) {
+      throw new Error(`invalid duration ${original}`);
+    }
+  }
+
+  return d;
+}
diff --git a/duration/jest.config.js b/duration/jest.config.js
new file mode 100644
index 000000000..6d5656840
--- /dev/null
+++ b/duration/jest.config.js
@@ -0,0 +1,16 @@
+/** @type {import('jest').Config} */
+const config = {
+  // We only test JS files once compiled with TypeScript
+  moduleFileExtensions: ["js"],
+  coverageDirectory: "coverage",
+  collectCoverage: true,
+  // If this is set to default (babel) rather than v8, tests fail with the edge
+  // runtime and the error "EvalError: Code generation from strings disallowed
+  // for this context". Tracking in
+  // https://github.com/vercel/edge-runtime/issues/250
+  coverageProvider: "v8",
+  verbose: true,
+  testEnvironment: "node",
+};
+
+export default config;
diff --git a/duration/package.json b/duration/package.json
new file mode 100644
index 000000000..6f3237815
--- /dev/null
+++ b/duration/package.json
@@ -0,0 +1,48 @@
+{
+  "name": "@arcjet/duration",
+  "version": "1.0.0-alpha.7",
+  "description": "Arcjet utilities for parsing duration strings",
+  "license": "Apache-2.0",
+  "homepage": "https://arcjet.com",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/arcjet/arcjet-js.git",
+    "directory": "ip"
+  },
+  "engines": {
+    "node": ">=18"
+  },
+  "type": "module",
+  "main": "./index.js",
+  "types": "./index.d.ts",
+  "files": [
+    "LICENSE",
+    "README.md",
+    "*.js",
+    "*.d.ts",
+    "*.ts",
+    "!*.config.js"
+  ],
+  "scripts": {
+    "prepublishOnly": "npm run build",
+    "build": "rollup --config rollup.config.js",
+    "lint": "eslint .",
+    "pretest": "npm run build",
+    "test": "NODE_OPTIONS=--experimental-vm-modules jest"
+  },
+  "dependencies": {},
+  "devDependencies": {
+    "@arcjet/eslint-config": "1.0.0-alpha.7",
+    "@arcjet/rollup-config": "1.0.0-alpha.7",
+    "@arcjet/tsconfig": "1.0.0-alpha.7",
+    "@jest/globals": "29.7.0",
+    "@rollup/wasm-node": "4.9.6",
+    "@types/node": "18.18.0",
+    "jest": "29.7.0",
+    "typescript": "5.3.3"
+  },
+  "publishConfig": {
+    "access": "public",
+    "tag": "latest"
+  }
+}
diff --git a/duration/rollup.config.js b/duration/rollup.config.js
new file mode 100644
index 000000000..79177f236
--- /dev/null
+++ b/duration/rollup.config.js
@@ -0,0 +1,3 @@
+import { createConfig } from "@arcjet/rollup-config";
+
+export default createConfig(import.meta.url);
diff --git a/duration/test/index.test.ts b/duration/test/index.test.ts
new file mode 100644
index 000000000..62966aa72
--- /dev/null
+++ b/duration/test/index.test.ts
@@ -0,0 +1,112 @@
+/**
+ * @jest-environment node
+ */
+import { describe, expect, test, afterEach, jest } from "@jest/globals";
+import { parse } from "../index";
+
+afterEach(() => {
+  jest.clearAllMocks();
+  jest.restoreAllMocks();
+});
+
+describe("parse", () => {
+  test("always returns 0 if the duration string is just 0", () => {
+    expect(parse("0")).toEqual(0);
+  });
+
+  test("fails if duration string is negative", () => {
+    expect(() => parse("-1s")).toThrow();
+  });
+
+  test("fails if duration string starts with a +", () => {
+    expect(() => parse("+1s")).toThrow();
+  });
+
+  test("fails if duration string does not start with a number", () => {
+    expect(() => parse("abc1000s")).toThrow();
+  });
+
+  test("fails if duration string is empty", () => {
+    expect(() => parse("")).toThrow();
+  });
+
+  test("fails if duration string is contains a decimal", () => {
+    expect(() => parse("1.5s")).toThrow();
+  });
+
+  test("fails if duration string uses unknown unit", () => {
+    expect(() => parse("1y")).toThrow();
+  });
+
+  test("fails if duration is not a string or number", () => {
+    expect(() => {
+      //@ts-expect-error
+      parse({});
+    }).toThrow();
+  });
+
+  test("returns duration number directly as seconds", () => {
+    expect(parse(1)).toEqual(1);
+    expect(parse(10000)).toEqual(10000);
+  });
+
+  test("fails if duration number overflows", () => {
+    expect(() => parse(4294967296)).toThrow();
+  });
+
+  test("fails if duration number is negative", () => {
+    expect(() => parse(-1)).toThrow();
+  });
+
+  test("fails if duration number is decimal", () => {
+    expect(() => parse(100.5)).toThrow();
+  });
+
+  test("parses seconds", () => {
+    expect(parse("1s")).toEqual(1);
+    expect(parse("1000s")).toEqual(1000);
+  });
+
+  test("fails if seconds overflow", () => {
+    expect(() => parse("4294967296s")).toThrow();
+  });
+
+  test("parses minutes into seconds", () => {
+    expect(parse("1m")).toEqual(60);
+    expect(parse("60m")).toEqual(3600);
+  });
+
+  test("fails if minutes-to-seconds overflow", () => {
+    expect(() => parse("71582789m")).toThrow();
+  });
+
+  test("parses hours into seconds", () => {
+    expect(parse("1h")).toEqual(3600);
+    expect(parse("24h")).toEqual(86400);
+  });
+
+  test("fails if hours-to-seconds overflow", () => {
+    expect(() => parse("1193047h")).toThrow();
+  });
+
+  test("parses days into seconds", () => {
+    expect(parse("1d")).toEqual(86400);
+    expect(parse("3d")).toEqual(259200);
+  });
+
+  test("fails if days-to-seconds overflow", () => {
+    expect(() => parse("49711d")).toThrow();
+  });
+
+  test("can combine multiple units", () => {
+    expect(parse("1h10m30s")).toEqual(4230);
+  });
+
+  test("fails if multiple units overflow", () => {
+    expect(() => parse("1193040h420m30s")).toThrow();
+  });
+
+  test("fails if missing unit on final value in multiple units", () => {
+    expect(() => parse("1d2h30")).toThrow();
+  });
+});
diff --git a/duration/tsconfig.json b/duration/tsconfig.json
new file mode 100644
index 000000000..95929e097
--- /dev/null
+++ b/duration/tsconfig.json
@@ -0,0 +1,4 @@
+{
+  "extends": "@arcjet/tsconfig/base",
+  "include": ["index.ts", "test/*.ts"]
+}
diff --git a/examples/nextjs-14-openai/app/api/chat/route.ts b/examples/nextjs-14-openai/app/api/chat/route.ts
index 8605554a4..f9957dbed 100644
--- a/examples/nextjs-14-openai/app/api/chat/route.ts
+++ b/examples/nextjs-14-openai/app/api/chat/route.ts
@@ -15,7 +15,7 @@ const aj = arcjet({
       mode: "LIVE",
       characteristics: ["ip.src"],
       refillRate: 40_000,
-      interval: 1 /* day */ * 24 /* hours */ * 60 /* minutes */ * 60 /* seconds */,
+      interval: "1d",
       capacity: 40_000,
     }),
   ],
diff --git a/package-lock.json b/package-lock.json
index 93540ccb7..73f2d86b5 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -40,6 +40,7 @@
       "license": "Apache-2.0",
       "dependencies": {
         "@arcjet/analyze": "1.0.0-alpha.7",
+        "@arcjet/duration": "1.0.0-alpha.7",
         "@arcjet/logger": "1.0.0-alpha.7",
         "@arcjet/protocol": "1.0.0-alpha.7"
       },
@@ -82,6 +83,24 @@
         "node": ">=18"
       }
     },
+    "duration": {
+      "name": "@arcjet/duration",
+      "version": "1.0.0-alpha.7",
+      "license": "Apache-2.0",
+      "devDependencies": {
+        "@arcjet/eslint-config": "1.0.0-alpha.7",
+        "@arcjet/rollup-config": "1.0.0-alpha.7",
+        "@arcjet/tsconfig": "1.0.0-alpha.7",
+        "@jest/globals": "29.7.0",
+        "@rollup/wasm-node": "4.9.6",
+        "@types/node": "18.18.0",
+        "jest": "29.7.0",
+        "typescript": "5.3.3"
+      },
+      "engines": {
+        "node": ">=18"
+      }
+    },
     "eslint-config": {
       "name": "@arcjet/eslint-config",
       "version": "1.0.0-alpha.7",
@@ -164,6 +183,10 @@
       "resolved": "analyze",
       "link": true
     },
+    "node_modules/@arcjet/duration": {
+      "resolved": "duration",
+      "link": true
+    },
     "node_modules/@arcjet/eslint-config": {
       "resolved": "eslint-config",
       "link": true
diff --git a/protocol/convert.ts b/protocol/convert.ts
index 4725adf17..0d311f388 100644
--- a/protocol/convert.ts
+++ b/protocol/convert.ts
@@ -522,7 +522,7 @@ export function ArcjetRuleToProtocol<Props extends { [key: string]: unknown }>(
           characteristics: rule.characteristics,
           algorithm: RateLimitAlgorithm.FIXED_WINDOW,
           max: rule.max,
-          window: rule.window,
+          windowInSeconds: rule.window,
         },
       },
     });
diff --git a/protocol/gen/es/decide/v1alpha1/decide_pb.d.ts b/protocol/gen/es/decide/v1alpha1/decide_pb.d.ts
index 321d9f134..48ced28af 100644
--- a/protocol/gen/es/decide/v1alpha1/decide_pb.d.ts
+++ b/protocol/gen/es/decide/v1alpha1/decide_pb.d.ts
@@ -673,9 +673,12 @@ export declare class RateLimitRule extends Message<RateLimitRule> {
    * The time window the rate limit applies to. This is a string value with a
    * sequence of decimal numbers, each with an optional fraction and a unit
    * suffix e.g. 1s for 1 second, 1h45m for 1 hour and 45 minutes, 1d for 1
-   * day. Valid time units are ns, us (or µs), ms, s, m, h, d, w, y.
+   * day. Valid time units are ns, us (or µs), ms, s, m, h.
+   *
+   * Deprecated: Use the window_in_seconds field instead.
    *
-   * @generated from field: string window = 4;
+   * @generated from field: string window = 4 [deprecated = true];
+   * @deprecated
    */
   window: string;
 
@@ -738,6 +741,16 @@ export declare class RateLimitRule extends Message<RateLimitRule> {
    */
   capacity: number;
 
+  /**
+   * The time window the rate limit applies to. This is an unsigned 32-bit
+   * integer value representing a number of seconds.
+   *
+   * Required by "fixed window" and unspecified algorithms.
+   *
+   * @generated from field: uint32 window_in_seconds = 12;
+   */
+  windowInSeconds: number;
+
   constructor(data?: PartialMessage<RateLimitRule>);
 
   static readonly runtime: typeof proto3;
diff --git a/protocol/gen/es/decide/v1alpha1/decide_pb.js b/protocol/gen/es/decide/v1alpha1/decide_pb.js
index 63b89c922..451a5e457 100644
--- a/protocol/gen/es/decide/v1alpha1/decide_pb.js
+++ b/protocol/gen/es/decide/v1alpha1/decide_pb.js
@@ -237,6 +237,7 @@ export const RateLimitRule = proto3.makeMessageType(
     { no: 8, name: "refill_rate", kind: "scalar", T: 13 /* ScalarType.UINT32 */ },
     { no: 9, name: "interval", kind: "scalar", T: 13 /* ScalarType.UINT32 */ },
     { no: 10, name: "capacity", kind: "scalar", T: 13 /* ScalarType.UINT32 */ },
+    { no: 12, name: "window_in_seconds", kind: "scalar", T: 13 /* ScalarType.UINT32 */ },
   ],
 );
 
diff --git a/protocol/index.ts b/protocol/index.ts
index b806da4e8..68ff2d64d 100644
--- a/protocol/index.ts
+++ b/protocol/index.ts
@@ -426,7 +426,7 @@ export interface ArcjetFixedWindowRateLimitRule<Props extends {}>
   match?: string;
   characteristics?: string[];
   max: number;
-  window: string;
+  window: number;
 }
 
 export interface ArcjetSlidingWindowRateLimitRule<Props extends {}>