markdown: Catch OverflowErrors in global times.

This also matches the except in the block above.

web/src/markdown.ts

@@ -1,4 +1,4 @@
-import {isValid} from "date-fns";
+import {getUnixTime, isValid} from "date-fns";
 import katex from "katex";
 import _ from "lodash";
 import assert from "minimalistic-assert";
@@ -580,7 +580,7 @@ function handleTimestamp(time_string: string): string {
     }
 
     const escaped_time = _.escape(time_string);
-    if (!isValid(timeobject)) {
+    if (!isValid(timeobject) || getUnixTime(timeobject) < 0) {
         // Unsupported time format: rerender accordingly.
 
         // We do not show an error on these formats in local echo because

zerver/lib/markdown/__init__.py

@@ -1455,7 +1455,7 @@ class Timestamp(markdown.inlinepatterns.Pattern):
         if timestamp.tzinfo:
             try:
                 timestamp = timestamp.astimezone(timezone.utc)
-            except ValueError:
+            except (ValueError, OverflowError):
                 error_element = Element("span")
                 error_element.set("class", "timestamp-error")
                 error_element.text = markdown.util.AtomicString(

zerver/tests/fixtures/markdown_test_cases.json

@@ -845,6 +845,13 @@
       "marked_expected_output": "<p><span>1969-12-31T00:00:00+32:00</span></p>",
       "text_content": "Invalid time format: 1969-12-31T00:00:00+32:00"
     },
+    {
+      "name": "timestamp_overflow",
+      "input": "<time:0001-01-01T01:00:00+02:00>",
+      "expected_output": "<p><span class=\"timestamp-error\">Invalid time format: 0001-01-01T01:00:00+02:00</span></p>",
+      "marked_expected_output": "<p><span>0001-01-01T01:00:00+02:00</span></p>",
+      "text_content": "Invalid time format: 0001-01-01T01:00:00+02:00"
+    },
     {
       "name": "timestamp_unix",
       "input": "Let's meet at <time:1496701800>.",