diff --git a/apps/api/lib/dayjs.ts b/apps/api/lib/dayjs.ts
new file mode 100644
index 00000000..e193b26c
--- /dev/null
+++ b/apps/api/lib/dayjs.ts
@@ -0,0 +1,6 @@
+import dayjsExtended from 'dayjs'
+import quarterOfYear from 'dayjs/plugin/quarterOfYear'
+
+dayjsExtended.extend(quarterOfYear)
+
+export { dayjsExtended }
diff --git a/apps/api/package.json b/apps/api/package.json
index 43b22f70..7207bbfe 100644
--- a/apps/api/package.json
+++ b/apps/api/package.json
@@ -16,6 +16,7 @@
     "@hono/clerk-auth": "^2.0.0",
     "@hono/zod-validator": "^0.2.2",
     "@prisma/client": "^5.15.0",
+    "dayjs": "^1.11.11",
     "hono": "^4.4.3",
     "zod": "^3.23.8"
   },
diff --git a/apps/api/v1/services/budget.service.ts b/apps/api/v1/services/budget.service.ts
index c4e36d37..f4505095 100644
--- a/apps/api/v1/services/budget.service.ts
+++ b/apps/api/v1/services/budget.service.ts
@@ -1,5 +1,11 @@
+import { dayjsExtended } from '@/lib/dayjs'
 import prisma from '@/lib/prisma'
-import { type Budget, BudgetUserPermission, type User } from '@prisma/client'
+import {
+  type Budget,
+  BudgetPeriodType,
+  BudgetUserPermission,
+  type User,
+} from '@prisma/client'
 import type { CreateBudget, UpdateBudget } from '../validation'
 import { inviteUserToBudget } from './budget-invitation.service'
 
@@ -89,6 +95,46 @@ export async function findBudget({ budgetId }: { budgetId: string }) {
   })
 }
 
+/**
+ * Given an anchor date and period type,
+ * calculate the start and end dates of the budget period.
+ * Example:
+ * - anchorDate: 2022-01-15
+ * - periodType: MONTHLY
+ * - startDate: 2022-01-01
+ * - endDate: 2022-01-31
+ */
+function calculateBudgetPeriodStartEndDates({
+  anchorDate,
+  type,
+}: {
+  anchorDate: Date
+  type: BudgetPeriodType
+}) {
+  switch (type) {
+    case BudgetPeriodType.MONTHLY:
+      return {
+        startDate: dayjsExtended(anchorDate).startOf('month').toDate(),
+        endDate: dayjsExtended(anchorDate).endOf('month').toDate(),
+      }
+    case BudgetPeriodType.QUARTERLY:
+      return {
+        startDate: dayjsExtended(anchorDate).startOf('quarter').toDate(),
+        endDate: dayjsExtended(anchorDate).endOf('quarter').toDate(),
+      }
+    case BudgetPeriodType.YEARLY:
+      return {
+        startDate: dayjsExtended(anchorDate).startOf('year').toDate(),
+        endDate: dayjsExtended(anchorDate).endOf('year').toDate(),
+      }
+    default:
+      return {
+        startDate: null,
+        endDate: null,
+      }
+  }
+}
+
 export async function createBudget({
   user,
   data,
@@ -105,6 +151,11 @@ export async function createBudget({
     inviteeEmails = [],
   } = data
 
+  const periodConfig = calculateBudgetPeriodStartEndDates({
+    anchorDate: new Date(),
+    type: period.type,
+  })
+
   const budget = await prisma.budget.create({
     data: {
       name,
@@ -115,8 +166,8 @@ export async function createBudget({
         create: {
           type: period.type,
           amount: period.amount,
-          startDate: period.startDate,
-          endDate: period.endDate,
+          startDate: period.endDate ?? periodConfig.startDate,
+          endDate: period.endDate ?? periodConfig.endDate,
         },
       },
       budgetUsers: {
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 809cc647..4dfb65fc 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -26,6 +26,9 @@ importers:
       '@prisma/client':
         specifier: ^5.15.0
         version: 5.15.0(prisma@5.15.0)
+      dayjs:
+        specifier: ^1.11.11
+        version: 1.11.11
       hono:
         specifier: ^4.4.3
         version: 4.4.3
@@ -443,6 +446,9 @@ packages:
   csstype@3.1.1:
     resolution: {integrity: sha512-DJR/VvkAvSZW9bTouZue2sSxDwdTN92uHjqeKVm+0dAqdfNykRzQ95tay8aXMBAAPpUiq4Qcug2L7neoRh2Egw==}
 
+  dayjs@1.11.11:
+    resolution: {integrity: sha512-okzr3f11N6WuqYtZSvm+F776mB41wRZMhKP+hc34YdW+KmtYYK9iqvHSwo2k9FEH3fhGXvOPV6yz2IcSrfRUDg==}
+
   debug@4.1.1:
     resolution: {integrity: sha512-pYAIzeRo8J6KPEaJ0VWOh5Pzkbw/RetuzehGM7QRRX5he4fPHx2rdKMB256ehJCkX+XRQm16eZLqLNS8RSZXZw==}
     deprecated: Debug versions >=3.2.0 <3.2.7 || >=4 <4.3.1 have a low-severity ReDos regression when used in a Node.js environment. It is recommended you upgrade to 3.2.7 or 4.3.1. (https://github.com/visionmedia/debug/issues/797)
@@ -1753,6 +1759,8 @@ snapshots:
 
   csstype@3.1.1: {}
 
+  dayjs@1.11.11: {}
+
   debug@4.1.1:
     dependencies:
       ms: 2.1.3