use local time instead of UTC, migrate.js, closes #131

Run `node migrate.js localtime data/*.json` to convert
existing `time` entries from UTC to your local timezone.

migrate.js

@@ -0,0 +1,34 @@
+import { existsSync } from 'fs';
+import { Low } from 'lowdb';
+import { JSONFile } from 'lowdb/node';
+import { datetime } from './util.js';
+
+const datetime_UTCtoLocalTimezone = async file => {
+  if (!existsSync(file))
+    return console.error('File does not exist:', file);
+  const db = new Low(new JSONFile(file));
+  await db.read();
+  db.data ||= {};
+  console.log('Migrating', file);
+  for (const user in db.data) {
+    for (const game in db.data[user]) {
+      const time1 = db.data[user][game].time;
+      const time1s = time1.endsWith('Z') ? time1 : time1 + ' UTC';
+      const time2 = datetime(new Date(time1s));
+      console.log([game, time1, time2]);
+      db.data[user][game].time = time2;
+    }
+  }
+  // console.log(db.data);
+  await db.write(); // write out json db
+};
+
+const args = process.argv.slice(2);
+if (args[0] == 'localtime') {
+  const files = args.slice(1);
+  console.log('Will convert UTC datetime to local timezone for', files);
+  files.forEach(datetime_UTCtoLocalTimezone);
+} else {
+  console.log('Usage: node migrate.js <cmd> <args>');
+  console.log('       node migrate.js localtime data/*.json');
+}

util.js

@@ -19,9 +19,9 @@ export const jsonDb = async file => {
 
 export const delay = ms => new Promise(resolve => setTimeout(resolve, ms));
 // date and time as UTC (no timezone offset) in nicely readable and sortable format, e.g., 2022-10-06 12:05:27.313
-export const datetime = (d = new Date()) => d.toISOString().replace('T', ' ').replace('Z', '');
+export const datetimeUTC = (d = new Date()) => d.toISOString().replace('T', ' ').replace('Z', '');
-// same as datetime() but for local timezone, e.g., UTC + 2h for the above in DE
+// same as datetimeUTC() but for local timezone, e.g., UTC + 2h for the above in DE
-export const datetimeLocal = (d = new Date()) => datetime(new Date(d.getTime() - new Date().getTimezoneOffset() * 60000));
+export const datetime = (d = new Date()) => datetimeUTC(new Date(d.getTime() - d.getTimezoneOffset() * 60000));
 export const filenamify = s => s.replaceAll(':', '.').replace(/[^a-z0-9 _\-.]/gi, '_'); // alternative: https://www.npmjs.com/package/filenamify - On Unix-like systems, / is reserved. On Windows, <>:"/\|?* along with trailing periods are reserved.
 
 export const handleSIGINT = () => process.on('SIGINT', () => { // e.g. when killed by Ctrl-C