diff --git a/src/custom-calendars/nepaliCalendar.ts b/src/custom-calendars/nepaliCalendar.ts
index 92d5ac0..fa65533 100644
--- a/src/custom-calendars/nepaliCalendar.ts
+++ b/src/custom-calendars/nepaliCalendar.ts
@@ -64,12 +64,18 @@ class NepaliCalendar extends Temporal.Calendar {
      *
      * A custom implementation of these methods is used to convert the calendar-space arguments to the ISO calendar.
      */
-    dateFromFields(fields: CalendarYMD): Temporal.PlainDate {
-        const { year, day, month } = _nepaliToIso({
-            year: fields.year,
-            month: fields.month,
-            day: fields.day,
-        })
+    dateFromFields(
+        fields: CalendarYMD,
+        options: Temporal.AssignmentOptions
+    ): Temporal.PlainDate {
+        const { year, day, month } = _nepaliToIso(
+            {
+                year: fields.year,
+                month: fields.month,
+                day: fields.day,
+            },
+            options
+        )
         return new Temporal.PlainDate(year, month, day, this)
     }
     yearMonthFromFields(fields: CalendarYMD): Temporal.PlainYearMonth {
@@ -96,7 +102,10 @@ const lastSupportedNepaliYear = Number(
     supportedNepaliYears[supportedNepaliYears.length - 1]
 )
 
-const _nepaliToIso = (fields: { day: number; year: number; month: number }) => {
+const _nepaliToIso = (
+    fields: { day: number; year: number; month: number },
+    { overflow }: Temporal.AssignmentOptions = {}
+) => {
     let { year: nepaliYear } = fields
 
     if (
@@ -109,6 +118,15 @@ const _nepaliToIso = (fields: { day: number; year: number; month: number }) => {
     }
     const { month: nepaliMonth, day: nepaliDay = 1 } = fields
 
+    if (
+        overflow === 'reject' &&
+        (nepaliMonth < 1 ||
+            nepaliMonth > 12 ||
+            nepaliDay > NEPALI_CALENDAR_DATA[nepaliYear][nepaliMonth])
+    ) {
+        throw new Error('Invalid date in Nepali calendar')
+    }
+
     let gregorianDayOfYear = 0
 
     let monthCounter = nepaliMonth
diff --git a/src/utils/validate-date-string.ts b/src/utils/validate-date-string.ts
index 084a060..8105192 100644
--- a/src/utils/validate-date-string.ts
+++ b/src/utils/validate-date-string.ts
@@ -3,53 +3,7 @@ import { Temporal } from '@js-temporal/polyfill'
 import { dhis2CalendarsMap } from '../constants/dhis2CalendarsMap'
 import type { SupportedCalendar } from '../types'
 import { extractDatePartsFromDateString } from './extract-date-parts-from-date-string'
-import { getCustomCalendarIfExists } from './helpers'
-
-type ValidateNepaliDateFn = (
-    year: number,
-    month: number,
-    day: number
-) => ValidationResult
-
-const validateNepaliDate: ValidateNepaliDateFn = (year, month, day) => {
-    const nepaliYearData = NEPALI_CALENDAR_DATA[year]
-    if (!nepaliYearData) {
-        return {
-            error: true,
-            validationCode: DateValidationResult.INVALID_DATE_IN_CALENDAR,
-            validationText: i18n.t(`Year {{year}} is out of range.`, { year }),
-        }
-    }
-
-    if (month < 1 || month > 12) {
-        return {
-            error: true,
-            validationCode: DateValidationResult.INVALID_DATE_IN_CALENDAR,
-            validationText: i18n.t(
-                `Month {{month}} is out of range | 1 <= {{month}} <= 12.`,
-                { month }
-            ),
-        }
-    }
-
-    const daysInMonth = nepaliYearData[month]
-
-    if (day < 1 || day > daysInMonth) {
-        return {
-            error: true,
-            validationCode: DateValidationResult.INVALID_DATE_IN_CALENDAR,
-            validationText: i18n.t(
-                `Day {{day}} is out of range | 1 <= {{day}} <= {{daysInMonth}}.`,
-                { day, daysInMonth }
-            ),
-        }
-    }
-
-    return {
-        error: false,
-        warning: false,
-    }
-}
+import { getCustomCalendarIfExists, isCustomCalendar } from './helpers'
 
 type ValidationOptions = {
     calendar?: SupportedCalendar
@@ -136,20 +90,17 @@ export const validateDateString: ValidateDateStringFn = (
             validationText: e?.message,
         }
     }
-    if (resolvedCalendar.toString() === 'nepali') {
-        // ToDo: double check why nepali can't just be handle with Temporal.PlainDate.from
-        return validateNepaliDate(
-            dateParts.year,
-            dateParts.month,
-            dateParts.day
-        )
-    }
 
     let date: Temporal.PlainDate
 
     // Will throw if the year, month or day is out of range
     try {
-        date = Temporal.PlainDate.from(
+        date = isCustomCalendar(resolvedCalendar)
+            ? Temporal.Calendar.from(resolvedCalendar).dateFromFields(
+                  dateParts,
+                  { overflow: 'reject' }
+              ) // need to be handled separately for custom calendars
+            : Temporal.PlainDate.from(
                   { ...dateParts, calendar: resolvedCalendar },
                   { overflow: 'reject' }
               )