diff --git a/packages/proto-signing/src/testdata/timestamp.json b/packages/proto-signing/src/testdata/timestamp.json
new file mode 100644
index 0000000000..9e4efad085
--- /dev/null
+++ b/packages/proto-signing/src/testdata/timestamp.json
@@ -0,0 +1,21 @@
+[
+  [0, 0, "1970-01-01T00:00:00.000000000Z"],
+  [0, 1, "1970-01-01T00:00:00.000000001Z"],
+  [0, 10, "1970-01-01T00:00:00.000000010Z"],
+  [0, 100, "1970-01-01T00:00:00.000000100Z"],
+  [0, 1000, "1970-01-01T00:00:00.000001000Z"],
+  [0, 10000, "1970-01-01T00:00:00.000010000Z"],
+  [0, 100000, "1970-01-01T00:00:00.000100000Z"],
+  [0, 1000000, "1970-01-01T00:00:00.001000000Z"],
+  [0, 10000000, "1970-01-01T00:00:00.010000000Z"],
+  [0, 100000000, "1970-01-01T00:00:00.100000000Z"],
+  [0, 999999999, "1970-01-01T00:00:00.999999999Z"],
+  [0, 1000000000, null],
+  [1, 0, "1970-01-01T00:00:01.000000000Z"],
+  [2, 0, "1970-01-01T00:00:02.000000000Z"],
+  [2, 6, "1970-01-01T00:00:02.000000006Z"],
+  [2, 6, "1970-01-01T00:00:02.000000006Z"],
+  [1657797740, 983000000, "2022-07-14T11:22:20.983000000Z"],
+  [-1, 0, "1969-12-31T23:59:59.000000000Z"],
+  [0, -1, null]
+]
diff --git a/packages/proto-signing/src/textual/valuerenderers.spec.ts b/packages/proto-signing/src/textual/valuerenderers.spec.ts
index 809b0fc0a7..9a85e8c432 100644
--- a/packages/proto-signing/src/textual/valuerenderers.spec.ts
+++ b/packages/proto-signing/src/textual/valuerenderers.spec.ts
@@ -6,6 +6,7 @@ import coinData from "../testdata/coin.json";
 import coinsData from "../testdata/coins.json";
 import decimals from "../testdata/decimals.json";
 import integers from "../testdata/integers.json";
+import timestampData from "../testdata/timestamp.json";
 import {
   DisplayUnit,
   formatBytes,
@@ -13,12 +14,15 @@ import {
   formatCoins,
   formatDecimal,
   formatInteger,
+  formatTimestamp,
 } from "./valuerenderers";
 
 type TestDataCoin = Array<[Coin, DisplayUnit, string]>;
 type TestDataCoins = Array<[Coin[], Record<string, DisplayUnit>, string]>;
 /** First argument is an array of bytes (0-255), second argument is the expected string */
 type TestDataBytes = Array<[number[], string]>;
+/** First argument is seconds, second argument is nanor and third argument is the expected string or null on error */
+type TestDataTimestamp = Array<[number, number, string | null]>;
 
 describe("valuerenderers", () => {
   describe("formatInteger", () => {
@@ -90,4 +94,25 @@ describe("valuerenderers", () => {
       }
     });
   });
+
+  describe("formatTimestamp", () => {
+    it("works", () => {
+      expect(formatTimestamp(0, 0)).toEqual("1970-01-01T00:00:00.000000000Z");
+      expect(formatTimestamp(0, 1)).toEqual("1970-01-01T00:00:00.000000001Z");
+      expect(formatTimestamp(1, 2)).toEqual("1970-01-01T00:00:01.000000002Z");
+      expect(formatTimestamp(5, 0)).toEqual("1970-01-01T00:00:05.000000000Z");
+
+      for (const [seconds, nanos, expected] of timestampData as TestDataTimestamp) {
+        if (expected === null) {
+          expect(() => formatTimestamp(seconds, nanos))
+            .withContext(`Input seconds=${seconds}, nanos=${nanos}`)
+            .toThrowError();
+        } else {
+          expect(formatTimestamp(seconds, nanos))
+            .withContext(`Input seconds=${seconds}, nanos=${nanos}`)
+            .toEqual(expected);
+        }
+      }
+    });
+  });
 });
diff --git a/packages/proto-signing/src/textual/valuerenderers.ts b/packages/proto-signing/src/textual/valuerenderers.ts
index 90d06275eb..0fe87ac13e 100644
--- a/packages/proto-signing/src/textual/valuerenderers.ts
+++ b/packages/proto-signing/src/textual/valuerenderers.ts
@@ -1,5 +1,5 @@
 import { toBase64 } from "@cosmjs/encoding";
-import { Decimal } from "@cosmjs/math";
+import { Decimal, Uint32 } from "@cosmjs/math";
 import { DenomUnit } from "cosmjs-types/cosmos/bank/v1beta1/bank";
 import { Coin } from "cosmjs-types/cosmos/base/v1beta1/coin";
 
@@ -40,3 +40,28 @@ export function formatCoins(input: Coin[], units: Record<string, DisplayUnit>):
 export function formatBytes(data: Uint8Array): string {
   return toBase64(data);
 }
+
+export interface DateWithNanoseconds extends Date {
+  /** Nanoseconds after the time stored in a vanilla Date (millisecond granularity) */
+  nanoseconds?: number;
+}
+
+function toRfc3339WithNanoseconds(dateTime: DateWithNanoseconds): string {
+  const millisecondIso = dateTime.toISOString();
+  const nanoseconds = dateTime.nanoseconds?.toString() ?? "";
+  return `${millisecondIso.slice(0, -1)}${nanoseconds.padStart(6, "0")}Z`;
+}
+
+function fromSeconds(seconds: number, nanos = 0): DateWithNanoseconds {
+  const checkedNanos = new Uint32(nanos).toNumber();
+  if (checkedNanos > 999_999_999) {
+    throw new Error("Nano seconds must not exceed 999999999");
+  }
+  const out: DateWithNanoseconds = new Date(seconds * 1000 + Math.floor(checkedNanos / 1000000));
+  out.nanoseconds = checkedNanos % 1000000;
+  return out;
+}
+
+export function formatTimestamp(seconds: number, nanos: number): string {
+  return toRfc3339WithNanoseconds(fromSeconds(seconds, nanos));
+}