[fix] format the code

lib/date.ts

@@ -2,10 +2,10 @@
  * Convert the date format of YYYY-MM-DD to American writing
  * @param date The date in format of YYYY-MM-DD.
  */
-export const normalizeDate = (date: string = "1970-01-01"): string => {
-  let [year, month, day] = date.split("-");
-  let month_num = parseInt(month);
-  let day_num = parseInt(day);
+export const normalizeDate = (date = "1970-01-01"): string => {
+  const [year, month, day] = date.split("-");
+  const month_num = Number.parseInt(month);
+  const day_num = Number.parseInt(day);
   const month_en: {
     [index: number]: string;
   } = {
@@ -43,3 +43,23 @@ export const getCurrentTime = (): {
     seconds: String(today.getSeconds()).padStart(2, "0"),
   };
 };
+
+export const convertDateToISO8601 = (dateString: string, timezoneOffset = 8): string => {
+  const date = new Date(dateString);
+
+  const offsetHours = timezoneOffset;
+  const offsetMinutes = offsetHours * 60;
+
+  date.setMinutes(date.getMinutes() + offsetMinutes);
+
+  const isoString = date.toISOString();
+
+  const datePart = isoString.split("T")[0];
+  const timePart = "00:00:00";
+
+  const offsetSign = offsetHours >= 0 ? "+" : "-";
+  const absOffsetHours = Math.abs(offsetHours).toString().padStart(2, "0");
+  const offsetString = `${offsetSign}${absOffsetHours}:00`;
+
+  return `${datePart}T${timePart}${offsetString}`;
+};

lib/post-process.ts

@@ -37,14 +37,15 @@ async function extractFrontmatters(filepath: string): Promise<TFrontmatter> {
 
 function readPostsDirectory(): string[] {
   const result: string[] = [];
-  fs.readdirSync(PostFilesDirectory).forEach((fileName) => {
+  const files = fs.readdirSync(PostFilesDirectory);
+  
+  for (const fileName of files) {
     const filePath = path.join(PostFilesDirectory, fileName);
     const fileStat = fs.statSync(filePath);
-
     if (fileStat.isFile() && fileName.endsWith(".md")) {
       result.push(filePath);
     }
-  });
+  }
   return result;
 }