feat: add timezone support for date code replacement

Author: bchrobot

.env.example

@@ -1,5 +1,6 @@
 ADMIN_SECRET=rDKs0Drx6Rmnqz09s1pDBYOvszpOkuPR
 FALLBACK_URL=http://isittuesday.co.uk/
+TIMEZONE=America/New_York
 
 SOURCE=google-sheets
 GOOGLE_SHEET_DOC_ID=06d8f872-6083-44c3-92a0-fbd82565f98f

src/config.ts

@@ -23,6 +23,7 @@ export interface AirtableConfig {
 interface Config extends CleanedEnvAccessors {
   adminSecret: string;
   fallbackUrl: string;
+  timezone: string;
   redisUrl?: string;
   source: LinkSourceType;
   googleConfig?: GoogleConfig;
@@ -44,6 +45,7 @@ const env = cleanEnv(process.env, {
   ADMIN_SECRET: str({}),
   FALLBACK_URL: url({}),
   FLY_REDIS_CACHE_URL: str({ default: undefined }),
+  TIMEZONE: str({}),
   SOURCE: linkSource({
     choices: Object.values(LinkSourceType),
     default: LinkSourceType.GoogleSheets,
@@ -88,6 +90,7 @@ export const config: Config = {
   ...envConfig,
   adminSecret: env.ADMIN_SECRET,
   fallbackUrl: env.FALLBACK_URL,
+  timezone: env.TIMEZONE,
   redisUrl: env.FLY_REDIS_CACHE_URL,
   source: env.SOURCE,
   googleConfig,

src/lib/shortener.ts

@@ -5,8 +5,9 @@ import request from 'superagent';
 
 import { Cache } from './cache';
 import { LinkRecord, LinkSource } from './types';
+import { config } from '../config';
 
-const currentYYMMDD = () => DateTime.now().toFormat('yyMMdd');
+const currentYYMMDD = () => DateTime.now().setZone(config.timezone).toFormat('yyMMdd');
 
 export interface LookupPathOptions {
   exactMatch: (matchingEntry: string) => void;