diff --git a/src/constants.ts b/src/constants.ts
new file mode 100644
index 0000000..dbd8aec
--- /dev/null
+++ b/src/constants.ts
@@ -0,0 +1,20 @@
+import { PeriodFormat } from "./types/time";
+
+export const lessonPeriods: readonly PeriodFormat[] = [
+  "8:30-9:10",
+  "9:20-10:00",
+  "10:15-10:55",
+  "11:10-11:50",
+  "12:00-12:40",
+  "12:50-13:30",
+] as const;
+
+export const WeekDays = [
+  "Monday",
+  "Tuesday",
+  "Wednesday",
+  "Thursday",
+  "Friday",
+  "Saturday",
+  "Sunday",
+] as const;
diff --git a/src/types/time.ts b/src/types/time.ts
new file mode 100644
index 0000000..cac0897
--- /dev/null
+++ b/src/types/time.ts
@@ -0,0 +1,5 @@
+import { WeekDays } from "../constants";
+
+export type PeriodFormat = `${number}:${number}-${number}:${number}`;
+
+export type WeekDay = typeof WeekDays[number];