fix: a swap deadline later than a date can hold is stated in words (closes #437)

decode() rendered the Deadline line with toISOString(), which throws on a
date past 275760-09-13, the last a JavaScript date can hold. A later
deadline, such as the uint256 maximum, therefore left the whole swap
undecoded, with nothing saying why. That line now reads
"After 275760-09-13 00:00:00 (no deadline in practice)".

Model: opus-5-5

README.md

@@ -1022,6 +1022,12 @@ unwraps the WETH it did not spend shows USDC. The token permission warning on
 the signature screen has its own amount wording, including `Unknown`; the
 SignApproval section below describes it.
 
+The swap's `Deadline` line is the router's deadline as a UTC date and time, e.g.
+`2026-02-27 08:25:51`. A JavaScript date reaches only to 275760-09-13 00:00:00
+UTC, so a later deadline, such as the `uint256` maximum, reads
+`After 275760-09-13 00:00:00 (no deadline in practice)` rather than leaving the
+whole swap undecoded.
+
 #### Partial USD totals
 
 Prices are fetched for the top 25 tokens only, so an address can hold assets the

TODO.md

@@ -45,6 +45,12 @@ but the review is broader than any of them.
 
 # Completed Steps
 
+- 2026-10-04: A swap whose deadline is later than a JavaScript date can hold is
+  decoded ([#437](https://git.eeqj.de/sneak/AutistMask/issues/437)). A date
+  reaches only to 275760-09-13, so a later deadline, such as the `uint256`
+  maximum, made the `Deadline` line throw, and the approval screen showed the
+  swap as an undecoded contract call with nothing saying why. That line now
+  reads `After 275760-09-13 00:00:00 (no deadline in practice)`.
 - 2026-10-04: The swap decoder reads two router zeros the way the router does
   ([#415](https://git.eeqj.de/sneak/AutistMask/issues/415)). A V2 exact-in
   `amountIn` of zero means an earlier step already sent the tokens to the pair;

src/shared/uniswap.js

@@ -724,10 +724,15 @@ function decode(data, toAddress, sources) {
 
         details.push({ label: "Steps", value: commandNames.join(" \u2192 ") });
 
+        // A JavaScript date reaches only to 275760-09-13 00:00:00 UTC. A
+        // later deadline, such as the uint256 maximum, makes an invalid date,
+        // and toISOString() throws on one, so that deadline is said in words.
         const deadlineDate = new Date(Number(deadline) * 1000);
         details.push({
             label: "Deadline",
-            value: deadlineDate.toISOString().replace("T", " ").slice(0, 19),
+            value: isNaN(deadlineDate.getTime())
+                ? "After 275760-09-13 00:00:00 (no deadline in practice)"
+                : deadlineDate.toISOString().replace("T", " ").slice(0, 19),
         });
 
         return {

tests/uniswap.test.js

@@ -554,6 +554,33 @@ describe("uniswap decoder", () => {
         );
     });
 
+    test("shows the deadline as a UTC date and time", () => {
+        const result = uniswap.decode(FIRST_SWAP_CALLDATA, ROUTER_ADDR);
+        expect(detail(result, "Deadline").value).toBe("2026-02-27 08:25:51");
+    });
+
+    // A JavaScript date cannot hold this deadline. It used to make the whole
+    // swap undecoded.
+    test("a deadline of the uint256 maximum is stated in words", () => {
+        const data = buildExecute(
+            "0x08", // V2_SWAP_EXACT_IN
+            [
+                encodeV2SwapExactIn(USER_ADDR, 1000000n, 500000000000000n, [
+                    USDT_ADDR,
+                    WETH_ADDR,
+                ]),
+            ],
+            2n ** 256n - 1n,
+        );
+
+        const result = uniswap.decode(data, ROUTER_ADDR);
+        expect(result).not.toBeNull();
+        expect(result.name).toBe("Swap USDT \u2192 WETH");
+        expect(detail(result, "Deadline").value).toBe(
+            "After 275760-09-13 00:00:00 (no deadline in practice)",
+        );
+    });
+
     test("formats permit amount when not unlimited", () => {
         const data = buildExecute(
             "0x0a",