diff --git a/app/global-error.tsx b/app/global-error.tsx
index b76eaa64..444a85cc 100644
--- a/app/global-error.tsx
+++ b/app/global-error.tsx
@@ -15,7 +15,10 @@ export default function GlobalError({
   }, [error]);
 
   return (
-    <html lang="sv">
+    <html lang="sv" translate="no">
+      <head>
+        <meta name="google" content="notranslate" />
+      </head>
       <body>
         <div className="flex min-h-screen items-center justify-center p-8">
           <div className="text-center space-y-4">
diff --git a/app/layout.tsx b/app/layout.tsx
index 478b4638..73551a47 100644
--- a/app/layout.tsx
+++ b/app/layout.tsx
@@ -46,8 +46,9 @@ export default function RootLayout({
   children: React.ReactNode;
 }>) {
   return (
-    <html lang="sv" suppressHydrationWarning className={`${geistSans.variable} ${geistMono.variable} ${fraunces.variable}`}>
+    <html lang="sv" translate="no" suppressHydrationWarning className={`${geistSans.variable} ${geistMono.variable} ${fraunces.variable}`}>
       <head>
+        <meta name="google" content="notranslate" />
         <link rel="apple-touch-icon" href="/icons/icon-192.png" />
         <script
           src="https://cdn.recapt.app/browser/glimt.js"
diff --git a/components/onboarding/Step3TaxRegistration.tsx b/components/onboarding/Step3TaxRegistration.tsx
index 3aa0e6a1..c85847c8 100644
--- a/components/onboarding/Step3TaxRegistration.tsx
+++ b/components/onboarding/Step3TaxRegistration.tsx
@@ -13,7 +13,7 @@ import { InfoTooltip } from '@/components/ui/info-tooltip'
 import { Loader2, ArrowRight, ArrowLeft, Check, CalendarDays } from 'lucide-react'
 import { cn } from '@/lib/utils'
 import { useToast } from '@/components/ui/use-toast'
-import { monthsBetween } from '@/lib/bookkeeping/validate-period-duration'
+import { monthsBetween, parseDateParts } from '@/lib/bookkeeping/validate-period-duration'
 import type { EntityType } from '@/types'
 
 const schema = z.object({
@@ -68,11 +68,8 @@ const monthNames = [
 ]
 
 function formatSwedishDate(dateStr: string): string {
-  const d = new Date(dateStr)
-  const day = d.getDate()
-  const month = monthNames[d.getMonth()].toLowerCase()
-  const year = d.getFullYear()
-  return `${day} ${month} ${year}`
+  const { year, month, day } = parseDateParts(dateStr)
+  return `${day} ${monthNames[month - 1].toLowerCase()} ${year}`
 }
 
 /**
@@ -180,28 +177,28 @@ export default function Step3TaxRegistration({
   // State for first-year start date selectors (month/year)
   const [startMonth, setStartMonth] = useState<number>(
     initialData.first_year_start
-      ? new Date(initialData.first_year_start).getMonth() + 1
+      ? parseDateParts(initialData.first_year_start).month
       : 0
   )
   const [startYear, setStartYear] = useState<number>(
     initialData.first_year_start
-      ? new Date(initialData.first_year_start).getFullYear()
+      ? parseDateParts(initialData.first_year_start).year
       : 0
   )
 
   // State for AB first-year end month selector
   const [abEndMonth, setAbEndMonth] = useState<number>(
     initialData.first_year_end
-      ? new Date(initialData.first_year_end).getMonth() + 1
+      ? parseDateParts(initialData.first_year_end).month
       : 12
   )
 
   // Parse first year start for date computations
   const parsedStart = useMemo(() => {
     if (!firstYearStart) return null
-    const d = new Date(firstYearStart)
-    if (isNaN(d.getTime())) return null
-    return { year: d.getFullYear(), month: d.getMonth() + 1 }
+    const parts = parseDateParts(firstYearStart)
+    if (isNaN(parts.year) || isNaN(parts.month)) return null
+    return { year: parts.year, month: parts.month }
   }, [firstYearStart])
 
   // Compute end date options for first year
@@ -220,8 +217,7 @@ export default function Step3TaxRegistration({
 
     if (data.is_first_fiscal_year && data.first_year_start && data.first_year_end) {
       // Derive start month from end date
-      const endDate = new Date(data.first_year_end)
-      const endMonth = endDate.getMonth() + 1
+      const endMonth = parseDateParts(data.first_year_end).month
       fiscalYearStartMonth = endMonth === 12 ? 1 : endMonth + 1
       firstStart = data.first_year_start
       firstEnd = data.first_year_end
diff --git a/lib/bookkeeping/validate-period-duration.ts b/lib/bookkeeping/validate-period-duration.ts
index 52a96846..73b38329 100644
--- a/lib/bookkeeping/validate-period-duration.ts
+++ b/lib/bookkeeping/validate-period-duration.ts
@@ -4,14 +4,25 @@
  * Normal ongoing periods are 12 months.
  */
 
+/**
+ * Parse a YYYY-MM-DD string into numeric parts without timezone issues.
+ * Using new Date(dateStr) is unsafe because it creates UTC midnight,
+ * but getDate()/getMonth()/getFullYear() return local-timezone values —
+ * shifting the date by -1 day in Western timezones.
+ */
+export function parseDateParts(dateStr: string): { year: number; month: number; day: number } {
+  const [year, month, day] = dateStr.split('-').map(Number)
+  return { year, month, day }
+}
+
 /**
  * Calculate the number of months between two dates (inclusive of partial months).
  * Assumes start is 1st of month and end is last of month.
  */
 export function monthsBetween(start: string, end: string): number {
-  const s = new Date(start)
-  const e = new Date(end)
-  return (e.getFullYear() - s.getFullYear()) * 12 + (e.getMonth() - s.getMonth()) + 1
+  const s = parseDateParts(start)
+  const e = parseDateParts(end)
+  return (e.year - s.year) * 12 + (e.month - s.month) + 1
 }
 
 /**
@@ -19,22 +30,23 @@ export function monthsBetween(start: string, end: string): number {
  * Returns null if valid, or an error message string if invalid.
  */
 export function validatePeriodDuration(start: string, end: string): string | null {
-  const startDate = new Date(start)
-  const endDate = new Date(end)
+  const startParts = parseDateParts(start)
+  const endParts = parseDateParts(end)
 
-  // end must be after start
-  if (endDate <= startDate) {
+  // end must be after start (YYYY-MM-DD strings are lexicographically orderable)
+  if (end <= start) {
     return 'Period end must be after period start'
   }
 
   // start must be 1st of month
-  if (startDate.getDate() !== 1) {
+  if (startParts.day !== 1) {
     return 'Period start must be the 1st of a month'
   }
 
   // end must be last day of month
-  const lastDayOfEndMonth = new Date(endDate.getFullYear(), endDate.getMonth() + 1, 0).getDate()
-  if (endDate.getDate() !== lastDayOfEndMonth) {
+  // new Date(year, 1-indexed-month, 0) gives the last day of that month
+  const lastDayOfEndMonth = new Date(endParts.year, endParts.month, 0).getDate()
+  if (endParts.day !== lastDayOfEndMonth) {
     return 'Period end must be the last day of a month'
   }