Enhance parseDate function to support additional time formats and improve UTC handling in tests

Author: ogroppo

src/helpers/parseDate.test.ts

@@ -107,6 +107,18 @@ describe("parseDate", () => {
       expect(parseDate("2000-02-21T00:00:01", { asUTC: true })).toStrictEqual(
         new Date("2000-02-21T00:00:01.000Z")
       );
+
+      expect(
+        parseDate("2000-02-21T00:00:01.001", { asUTC: true })
+      ).toStrictEqual(new Date("2000-02-21T00:00:01.001Z"));
+
+      expect(
+        parseDate("2000-02-21T00:00:01.001Z") // no asUTC
+      ).toStrictEqual(new Date("2000-02-21T00:00:01.001Z"));
+
+      expect(
+        parseDate("2000-02-21T00:00:01.001Z", { asUTC: true }) // asUTC
+      ).toStrictEqual(new Date("2000-02-21T00:00:01.001Z"));
     });
   });
 

src/helpers/parseDate.ts

@@ -6,6 +6,9 @@ import { isNumber } from "../validators/isNumber";
 import { isString } from "../validators/isString";
 
 const partialDateRegex = /^\d{4}(-\d{2})?(-\d{2})?$/;
+// Matches complete date-time without timezone: YYYY-MM-DD or YYYY-MM-DDTHH:MM:SS or YYYY-MM-DDTHH:MM:SS.mmm
+// Does NOT match dates ending with Z or +/-HH:MM timezone offsets
+const noTimezoneRegex = /^(?!.*(?:Z|[+-]\d{2}:?\d{2})).+$/;
 
 /**
  *
@@ -42,17 +45,21 @@ export const parseDate = (
       }T00:00:00`;
     }
 
+    // Now check that time is complete (JS can parse HH:mm but not HH)
     const [date, time] = arg.split("T");
-    // 8 as in "HH:MM:SS"
-    if (time.length < 8) {
+    // 8 as in "HH:MM:SS" (actually, just HH:mm would be enough, but better be safe)
+    // time is undefined for crappy strings like "hello-I-am-a-date"
+    if (time?.length < 8) {
       arg = `${date}T${time}${"00:00:00".slice(time.length)}`;
     }
 
-    if (options?.asUTC) {
+    if (options?.asUTC && noTimezoneRegex.test(arg)) {
       arg += "Z"; // In this case, force UTC
     }
   }
 
+  console.log(arg);
+
   const date = new Date(arg!); // ! => isEmpty cannot narrow type
 
   if (!isJsDate(date)) return;

src/validators/isSameUTCDay.ts

@@ -19,6 +19,7 @@ export const isSameUTCDay = (
   const date2UTC = parseDate(date2Input, { asUTC: true });
   if (!date1UTC || !date2UTC) return false;
 
+  console.log(date1UTC.toISOString(), date2UTC.toISOString());
   return (
     date1UTC.getUTCFullYear() === date2UTC.getUTCFullYear() &&
     date1UTC.getUTCMonth() === date2UTC.getUTCMonth() &&