diff --git a/package-lock.json b/package-lock.json
index af83eac..f52cab1 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
     "name": "@time-loop/hot-formula-parser",
-    "version": "4.1.0",
+    "version": "4.2.0",
     "lockfileVersion": 3,
     "requires": true,
     "packages": {
         "": {
             "name": "@time-loop/hot-formula-parser",
-            "version": "4.1.0",
+            "version": "4.2.0",
             "dependencies": {
                 "@formulajs/formulajs": "^2.3.0",
                 "json5": "^2.2.3",
diff --git a/package.json b/package.json
index 7668777..b0006c4 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
     "name": "@time-loop/hot-formula-parser",
-    "version": "4.1.2",
+    "version": "4.2.0",
     "description": "Formula parser",
     "type": "commonjs",
     "main": "dist/index.js",
diff --git a/src/clickup/formulajsProxy.ts b/src/clickup/formulajsProxy.ts
new file mode 100644
index 0000000..18e8887
--- /dev/null
+++ b/src/clickup/formulajsProxy.ts
@@ -0,0 +1,52 @@
+import * as formulajs from '@formulajs/formulajs';
+
+const hasNil = (...args: unknown[]) =>
+    args.some((arg) => arg === null || arg === undefined || arg === '' || arg === false);
+const nullToZero = (arg: unknown) => (hasNil(arg) ? 0 : arg);
+
+const overrides = {
+    DATE: (year: unknown, month: unknown, day: unknown) =>
+        hasNil(year, month, day) ? Number.NaN : formulajs.DATE(year, month, day),
+    DATEVALUE: (dateText: unknown) => (hasNil(dateText) ? Number.NaN : formulajs.DATEVALUE(dateText)),
+    DAY: (date: unknown) => (hasNil(date) ? Number.NaN : formulajs.DAY(date)),
+    DAYS: (startDate: unknown, endDate: unknown) =>
+        hasNil(startDate, endDate) ? Number.NaN : formulajs.DAYS(startDate, endDate),
+    DAYS360: (startDate: unknown, endDate: unknown, method: unknown) =>
+        hasNil(startDate, endDate) ? Number.NaN : formulajs.DAYS360(startDate, endDate, method),
+    EDATE: (startDate: unknown, months: unknown) =>
+        hasNil(startDate) ? Number.NaN : formulajs.EDATE(startDate, nullToZero(months)),
+    EOMONTH: (startDate: unknown, months: unknown) =>
+        hasNil(startDate) ? Number.NaN : formulajs.EOMONTH(startDate, nullToZero(months)),
+    HOUR: (date: unknown) => (hasNil(date) ? Number.NaN : formulajs.HOUR(date)),
+    INTERVAL: (seconds: unknown) => formulajs.INTERVAL(nullToZero(seconds)),
+    ISOWEEKNUM: (date: unknown) => (hasNil(date) ? Number.NaN : formulajs.ISOWEEKNUM(date)),
+    MINUTE: (serialNumber: unknown) => (hasNil(serialNumber) ? Number.NaN : formulajs.MINUTE(serialNumber)),
+    MONTH: (date: unknown) => (hasNil(date) ? Number.NaN : formulajs.MONTH(date)),
+    SECOND: (serialNumber: unknown) => (hasNil(serialNumber) ? Number.NaN : formulajs.SECOND(serialNumber)),
+    TIME: (hour: unknown, minute: unknown, second: unknown) =>
+        hasNil(hour, minute, second) ? Number.NaN : formulajs.TIME(hour, minute, second),
+    TIMEVALUE: (timeText: unknown) => (hasNil(timeText) ? Number.NaN : formulajs.TIMEVALUE(timeText)),
+    WEEKDAY: (serialNumber: unknown, returnType: unknown) =>
+        hasNil(serialNumber) ? Number.NaN : formulajs.WEEKDAY(serialNumber, returnType),
+    WEEKNUM: (serialNumber: unknown, returnType: unknown) =>
+        hasNil(serialNumber) ? Number.NaN : formulajs.WEEKNUM(serialNumber, returnType),
+    YEAR: (date: unknown) => (hasNil(date) ? Number.NaN : formulajs.YEAR(date)),
+    YEARFRAC: (startDate: unknown, endDate: unknown, basis: unknown) =>
+        hasNil(startDate, endDate) ? Number.NaN : formulajs.YEARFRAC(startDate, endDate, basis),
+    WORKDAY: (startDate: unknown, days: unknown, holidays: unknown) =>
+        hasNil(startDate) ? Number.NaN : formulajs.WORKDAY(startDate, nullToZero(days), holidays),
+    NETWORKDAYS: (startDate: unknown, endDate: unknown, holidays: unknown) =>
+        hasNil(startDate, endDate) ? Number.NaN : formulajs.NETWORKDAYS(startDate, endDate, holidays),
+};
+
+export const formulajsProxy = new Proxy(formulajs, {
+    get: (target, prop) => {
+        if (prop in overrides) {
+            return overrides[prop as keyof typeof overrides];
+        }
+        if (prop in target) {
+            return target[prop];
+        }
+        return null;
+    },
+});
diff --git a/src/evaluate-by-operator/operator/formula-function.js b/src/evaluate-by-operator/operator/formula-function.js
index 8f2a11b..ef58f2b 100644
--- a/src/evaluate-by-operator/operator/formula-function.js
+++ b/src/evaluate-by-operator/operator/formula-function.js
@@ -1,4 +1,4 @@
-import * as formulajs from '@formulajs/formulajs';
+import { formulajsProxy as formulajs } from '../../clickup/formulajsProxy';
 import SUPPORTED_FORMULAS from '../../supported-formulas';
 import { ERROR_NAME } from '../../error';
 
diff --git a/src/helper/number.js b/src/helper/number.js
index 8b902cd..a2da138 100644
--- a/src/helper/number.js
+++ b/src/helper/number.js
@@ -1,4 +1,4 @@
-import * as formulajs from '@formulajs/formulajs';
+import { formulajsProxy as formulajs } from '../clickup/formulajsProxy';
 import splitFormula from './formula';
 import { getNumberOfDaysSinceEpoch, isDate } from './date';
 
diff --git a/test/integration/parsing/formula/date-time.js b/test/integration/parsing/formula/date-time.test.js
similarity index 59%
rename from test/integration/parsing/formula/date-time.js
rename to test/integration/parsing/formula/date-time.test.js
index 94a8a1c..4721b1c 100644
--- a/test/integration/parsing/formula/date-time.js
+++ b/test/integration/parsing/formula/date-time.test.js
@@ -3,7 +3,10 @@ import Parser from '../../../../src/parser';
 
 describe('.parse() date & time formulas', () => {
     it.each([new Parser(), ClickUpParser.create()])('DATE', (parser) => {
-        expect(parser.parse('DATE()')).toMatchObject({ error: '#VALUE!', result: null });
+        expect(parser.parse('DATE()')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('DATE(null, 5, 12)')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('DATE(2001, null, 12)')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('DATE(2001, 5, null)')).toMatchObject({ error: null, result: Number.NaN });
 
         const { error, result } = parser.parse('DATE(2001, 5, 12)');
 
@@ -14,85 +17,107 @@ describe('.parse() date & time formulas', () => {
     });
 
     it.each([new Parser(), ClickUpParser.create()])('DATEVALUE', (parser) => {
-        expect(parser.parse('DATEVALUE()')).toMatchObject({ error: '#VALUE!', result: null });
+        expect(parser.parse('DATEVALUE()')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('DATEVALUE(null)')).toMatchObject({ error: null, result: Number.NaN });
         expect(parser.parse('DATEVALUE("1/1/1900")')).toMatchObject({ error: null, result: 1 });
         expect(parser.parse('DATEVALUE("1/1/2000")')).toMatchObject({ error: null, result: 36526 });
     });
 
     it.each([new Parser(), ClickUpParser.create()])('DAY', (parser) => {
-        expect(parser.parse('DAY()')).toMatchObject({ error: '#VALUE!', result: null });
+        expect(parser.parse('DAY()')).toMatchObject({ error: null, result: Number.NaN });
         expect(parser.parse('DAY(1)')).toMatchObject({ error: null, result: 1 });
         expect(parser.parse('DAY(2958465)')).toMatchObject({ error: null, result: 31 });
         expect(parser.parse('DAY("2958465")')).toMatchObject({ error: null, result: 31 });
+        expect(parser.parse('DAY(null)')).toMatchObject({ error: null, result: Number.NaN });
     });
 
     it.each([new Parser(), ClickUpParser.create()])('DAYS', (parser) => {
-        expect(parser.parse('DAYS()')).toMatchObject({ error: '#VALUE!', result: null });
-        expect(parser.parse('DAYS(1)')).toMatchObject({ error: '#VALUE!', result: null });
+        expect(parser.parse('DAYS()')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('DAYS(1)')).toMatchObject({ error: null, result: Number.NaN });
         expect(parser.parse('DAYS(1, 6)')).toMatchObject({ error: null, result: -5 });
         expect(parser.parse('DAYS("1/2/2000", "1/10/2001")')).toMatchObject({ error: null, result: -374 });
+        expect(parser.parse('DAYS(null, 1)')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('DAYS(1, null)')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('DAYS(null, null)')).toMatchObject({ error: null, result: Number.NaN });
     });
 
     it.each([new Parser(), ClickUpParser.create()])('DAYS360', (parser) => {
-        expect(parser.parse('DAYS360()')).toMatchObject({ error: '#VALUE!', result: null });
-        expect(parser.parse('DAYS360(1)')).toMatchObject({ error: '#VALUE!', result: null });
+        expect(parser.parse('DAYS360()')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('DAYS360(1)')).toMatchObject({ error: null, result: Number.NaN });
         expect(parser.parse('DAYS360(1, 6)')).toMatchObject({ error: '#VALUE!', result: null });
         expect(parser.parse('DAYS360("1/1/1901", "2/1/1901", TRUE)')).toMatchObject({ error: null, result: 30 });
         expect(parser.parse('DAYS360("1/1/1901", "12/31/1901", FALSE)')).toMatchObject({ error: null, result: 360 });
+        expect(parser.parse('DAYS360(null, "1/1/1901")')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('DAYS360("1/1/1901", null)')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('DAYS360(null, null)')).toMatchObject({ error: null, result: Number.NaN });
     });
 
     it.each([new Parser(), ClickUpParser.create()])('EDATE', (parser) => {
-        expect(parser.parse('EDATE()')).toMatchObject({ error: '#VALUE!', result: null });
-        expect(parser.parse('EDATE(1)')).toMatchObject({ error: '#VALUE!', result: null });
+        expect(parser.parse('EDATE()')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('EDATE(1)')).toMatchObject({ error: null, result: 1 });
         expect(parser.parse('EDATE("1/1/1900", 1)')).toMatchObject({ error: null, result: 32 });
+        expect(parser.parse('EDATE(null, 1)')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('EDATE("1/1/1900", null)')).toMatchObject({ error: null, result: 1 });
+        expect(parser.parse('EDATE(null, null)')).toMatchObject({ error: null, result: Number.NaN });
     });
 
     it.each([new Parser(), ClickUpParser.create()])('EOMONTH', (parser) => {
-        expect(parser.parse('EOMONTH()')).toMatchObject({ error: '#VALUE!', result: null });
-        expect(parser.parse('EOMONTH(1)')).toMatchObject({ error: '#VALUE!', result: null });
+        expect(parser.parse('EOMONTH()')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('EOMONTH(1)')).toMatchObject({ error: null, result: 31 });
         expect(parser.parse('EOMONTH("1/1/1900", 1)')).toMatchObject({ error: null, result: 59 });
+        expect(parser.parse('EOMONTH(null, 1)')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('EOMONTH("1/1/1900", null)')).toMatchObject({ error: null, result: 31 });
+        expect(parser.parse('EOMONTH(null, null)')).toMatchObject({ error: null, result: Number.NaN });
     });
 
     it.each([new Parser(), ClickUpParser.create()])('HOUR', (parser) => {
-        expect(parser.parse('HOUR()')).toMatchObject({ error: '#VALUE!', result: null });
+        expect(parser.parse('HOUR()')).toMatchObject({ error: null, result: Number.NaN });
         expect(parser.parse('HOUR("1/1/1900 16:33")')).toMatchObject({ error: null, result: 16 });
+        expect(parser.parse('HOUR(null)')).toMatchObject({ error: null, result: Number.NaN });
     });
 
     it.each([new Parser(), ClickUpParser.create()])('INTERVAL', (parser) => {
-        expect(parser.parse('INTERVAL()')).toMatchObject({ error: '#VALUE!', result: null });
+        expect(parser.parse('INTERVAL()')).toMatchObject({ error: null, result: 'PT' });
         expect(parser.parse('INTERVAL(0)')).toMatchObject({ error: null, result: 'PT' });
         expect(parser.parse('INTERVAL(1)')).toMatchObject({ error: null, result: 'PT1S' });
         expect(parser.parse('INTERVAL(60)')).toMatchObject({ error: null, result: 'PT1M' });
         expect(parser.parse('INTERVAL(10000000)')).toMatchObject({ error: null, result: 'P3M25DT17H46M40S' });
+        expect(parser.parse('INTERVAL(null)')).toMatchObject({ error: null, result: 'PT' });
     });
 
     it.each([new Parser(), ClickUpParser.create()])('ISOWEEKNUM', (parser) => {
-        expect(parser.parse('ISOWEEKNUM()')).toMatchObject({ error: '#VALUE!', result: null });
+        expect(parser.parse('ISOWEEKNUM()')).toMatchObject({ error: null, result: Number.NaN });
         expect(parser.parse('ISOWEEKNUM("1/8/1901")')).toMatchObject({ error: null, result: 2 });
         expect(parser.parse('ISOWEEKNUM("6/6/1902")')).toMatchObject({ error: null, result: 23 });
+        expect(parser.parse('ISOWEEKNUM(null)')).toMatchObject({ error: null, result: Number.NaN });
     });
 
     it.each([new Parser(), ClickUpParser.create()])('MINUTE', (parser) => {
-        expect(parser.parse('MINUTE()')).toMatchObject({ error: '#VALUE!', result: null });
+        expect(parser.parse('MINUTE()')).toMatchObject({ error: null, result: Number.NaN });
         expect(parser.parse('MINUTE("1/1/1901 1:01")')).toMatchObject({ error: null, result: 1 });
         expect(parser.parse('MINUTE("1/1/1901 15:36")')).toMatchObject({ error: null, result: 36 });
+        expect(parser.parse('MINUTE(null)')).toMatchObject({ error: null, result: Number.NaN });
     });
 
     it.each([new Parser(), ClickUpParser.create()])('MONTH', (parser) => {
-        expect(parser.parse('MONTH()')).toMatchObject({ error: '#VALUE!', result: null });
+        expect(parser.parse('MONTH()')).toMatchObject({ error: null, result: Number.NaN });
         expect(parser.parse('MONTH("2/1/1901")')).toMatchObject({ error: null, result: 2 });
         expect(parser.parse('MONTH("10/1/1901")')).toMatchObject({ error: null, result: 10 });
+        expect(parser.parse('MONTH(null)')).toMatchObject({ error: null, result: Number.NaN });
     });
 
     it.each([new Parser(), ClickUpParser.create()])('NETWORKDAYS', (parser) => {
-        expect(parser.parse('NETWORKDAYS()')).toMatchObject({ error: '#VALUE!', result: null });
-        expect(parser.parse('NETWORKDAYS("2/1/1901")')).toMatchObject({ error: '#VALUE!', result: null });
+        expect(parser.parse('NETWORKDAYS()')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('NETWORKDAYS("2/1/1901")')).toMatchObject({ error: null, result: Number.NaN });
         expect(parser.parse('NETWORKDAYS("2013-12-04", "2013-12-05")')).toMatchObject({ error: null, result: 2 });
         expect(parser.parse('NETWORKDAYS("2013-11-04", "2013-12-05")')).toMatchObject({ error: null, result: 24 });
         expect(parser.parse('NETWORKDAYS("10/1/2012", "3/1/2013", [\'11/22/2012\'])')).toMatchObject({
             error: null,
             result: 109,
         });
+        expect(parser.parse('NETWORKDAYS(null, "2013-12-05")')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('NETWORKDAYS("2013-12-05", null)')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('NETWORKDAYS(null, null)')).toMatchObject({ error: null, result: Number.NaN });
     });
 
     it.each([new Parser(), ClickUpParser.create()])('NOW', (parser) => {
@@ -104,26 +129,31 @@ describe('.parse() date & time formulas', () => {
     });
 
     it.each([new Parser(), ClickUpParser.create()])('SECOND', (parser) => {
-        expect(parser.parse('SECOND()')).toMatchObject({ error: '#VALUE!', result: null });
+        expect(parser.parse('SECOND()')).toMatchObject({ error: null, result: Number.NaN });
         expect(parser.parse('SECOND("2/1/1901 13:33:12")')).toMatchObject({ error: null, result: 12 });
+        expect(parser.parse('SECOND(null)')).toMatchObject({ error: null, result: Number.NaN });
     });
 
     it.each([new Parser(), ClickUpParser.create()])('TIME', (parser) => {
-        expect(parser.parse('TIME()')).toMatchObject({ error: '#VALUE!', result: null });
-        expect(parser.parse('TIME(0)')).toMatchObject({ error: '#VALUE!', result: null });
-        expect(parser.parse('TIME(0, 0)')).toMatchObject({ error: '#VALUE!', result: null });
+        expect(parser.parse('TIME()')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('TIME(0)')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('TIME(0, 0)')).toMatchObject({ error: null, result: Number.NaN });
         expect(parser.parse('TIME(0, 0, 0)')).toMatchObject({ error: null, result: 0 });
         expect(parser.parse('TIME(1, 1, 1)')).toMatchObject({ error: null, result: 0.04237268518518519 });
         expect(parser.parse('TIME(24, 0, 0)')).toMatchObject({ error: null, result: 1 });
+        expect(parser.parse('TIME(null, 0, 0)')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('TIME(0, null, 0)')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('TIME(0, 0, null)')).toMatchObject({ error: null, result: Number.NaN });
     });
 
     it.each([new Parser(), ClickUpParser.create()])('TIMEVALUE', (parser) => {
-        expect(parser.parse('TIMEVALUE()')).toMatchObject({ error: '#VALUE!', result: null });
+        expect(parser.parse('TIMEVALUE()')).toMatchObject({ error: null, result: Number.NaN });
         expect(parser.parse('TIMEVALUE("1/1/1900 00:00:00")')).toMatchObject({ error: null, result: 0 });
         expect(parser.parse('TIMEVALUE("1/1/1900 23:00:00")')).toMatchObject({
             error: null,
             result: 0.9583333333333334,
         });
+        expect(parser.parse('TIMEVALUE(null)')).toMatchObject({ error: null, result: Number.NaN });
     });
 
     it.each([new Parser(), ClickUpParser.create()])('TODAY', (parser) => {
@@ -135,20 +165,25 @@ describe('.parse() date & time formulas', () => {
     });
 
     it.each([new Parser(), ClickUpParser.create()])('WEEKDAY', (parser) => {
-        expect(parser.parse('WEEKDAY()')).toMatchObject({ error: '#VALUE!', result: null });
+        expect(parser.parse('WEEKDAY()')).toMatchObject({ error: null, result: Number.NaN });
         expect(parser.parse('WEEKDAY("1/1/1901")')).toMatchObject({ error: null, result: 3 });
         expect(parser.parse('WEEKDAY("1/1/1901", 2)')).toMatchObject({ error: null, result: 2 });
+        expect(parser.parse('WEEKDAY(null)')).toMatchObject({ error: null, result: Number.NaN });
     });
 
     it.each([new Parser(), ClickUpParser.create()])('WEEKNUM', (parser) => {
-        expect(parser.parse('WEEKNUM()')).toMatchObject({ error: '#VALUE!', result: null });
+        expect(parser.parse('WEEKNUM()')).toMatchObject({ error: null, result: Number.NaN });
         expect(parser.parse('WEEKNUM("2/1/1900")')).toMatchObject({ error: null, result: 5 });
         expect(parser.parse('WEEKNUM("2/1/1909", 2)')).toMatchObject({ error: null, result: 6 });
+        expect(parser.parse('WEEKNUM(null)')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('WEEKNUM("a")')).toMatchObject({ error: '#VALUE!', result: null });
     });
 
     it.each([new Parser(), ClickUpParser.create()])('WORKDAY', (parser) => {
-        expect(parser.parse('WORKDAY()')).toMatchObject({ error: '#VALUE!', result: null });
-        expect(parser.parse('WORKDAY("1/1/1900")')).toMatchObject({ error: '#VALUE!', result: null });
+        expect(parser.parse('WORKDAY()')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('WORKDAY("1/1/1900")')).toMatchObject({ error: null, result: new Date(1900, 0, 1) });
+        expect(parser.parse('WORKDAY(null)')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('WORKDAY("1/1/1900", null)')).toMatchObject({ error: null, result: new Date(1900, 0, 1) });
 
         const { result, error } = parser.parse('WORKDAY("1/1/1900", 1)');
 
@@ -157,17 +192,21 @@ describe('.parse() date & time formulas', () => {
     });
 
     it.each([new Parser(), ClickUpParser.create()])('YEAR', (parser) => {
-        expect(parser.parse('YEAR()')).toMatchObject({ error: '#VALUE!', result: null });
+        expect(parser.parse('YEAR()')).toMatchObject({ error: null, result: Number.NaN });
         expect(parser.parse('YEAR("1/1/1904")')).toMatchObject({ error: null, result: 1904 });
         expect(parser.parse('YEAR("12/12/2001")')).toMatchObject({ error: null, result: 2001 });
+        expect(parser.parse('YEAR(null)')).toMatchObject({ error: null, result: Number.NaN });
     });
 
     it.each([new Parser(), ClickUpParser.create()])('YEARFRAC', (parser) => {
-        expect(parser.parse('YEARFRAC()')).toMatchObject({ error: '#VALUE!', result: null });
-        expect(parser.parse('YEARFRAC("1/1/1904")')).toMatchObject({ error: '#VALUE!', result: null });
+        expect(parser.parse('YEARFRAC()')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('YEARFRAC("1/1/1904")')).toMatchObject({ error: null, result: Number.NaN });
         expect(parser.parse('YEARFRAC("1/1/1900", "1/2/1900")')).toMatchObject({
             error: null,
             result: 0.002777777777777778,
         });
+        expect(parser.parse('YEARFRAC(null, "1/2/1900")')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('YEARFRAC("1/1/1900", null)')).toMatchObject({ error: null, result: Number.NaN });
+        expect(parser.parse('YEARFRAC(null, null)')).toMatchObject({ error: null, result: Number.NaN });
     });
 });