diff --git a/.vscode/settings.json b/.vscode/settings.json
index 7185d2b..b873f92 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -1,6 +1,7 @@
 {
   "deno.enable": true,
   "cSpell.words": [
+    "BYDAY",
     "CALSCALE",
     "DTEND",
     "DTSTAMP",
diff --git a/mod.ts b/mod.ts
index 6169c08..c958a78 100644
--- a/mod.ts
+++ b/mod.ts
@@ -1,2 +1,3 @@
 export { Calendar, Event } from './main.ts';
 export type { EventConfig } from './main.ts';
+export type { Day, RecurrenceRule } from './rrule.ts';
diff --git a/rrule.ts b/rrule.ts
index 057c93d..e22bd0e 100644
--- a/rrule.ts
+++ b/rrule.ts
@@ -5,20 +5,24 @@ export interface RecurrenceRule {
   until?: DateData;
   interval?: number;
   count?: number;
+  byDay?: Day[];
 }
 
 export function parseRRule(rrule: RecurrenceRule | undefined) {
   if (rrule === undefined) return;
 
-  const { freq, until, interval, count } = rrule;
+  const { freq, until, interval, count, byDay } = rrule;
 
   return [
     ['FREQ', freq],
     ['UNTIL', parseDate(until)],
     ['INTERVAL', interval],
     ['COUNT', count],
+    ['BYDAY', byDay ? byDay.join() : undefined],
   ]
     .filter(line => line[1] !== undefined)
     .map(line => `${line[0]}=${line[1]};`)
     .join('');
 }
+
+export type Day = 'MO' | 'TU' | 'WE' | 'TH' | 'FR' | 'SA' | 'SU';