diff --git a/common/src/dateJump/GregorianJumper.tsx b/common/src/dateJump/GregorianJumper.tsx
new file mode 100644
index 0000000..252589e
--- /dev/null
+++ b/common/src/dateJump/GregorianJumper.tsx
@@ -0,0 +1,43 @@
+import {DateJumperProps} from './base';
+import React from 'react';
+import {gregorianJDN, jdnGregorian} from '../gregorian';
+
+export default function GregorianJumper({minJDN, maxJDN, todayJDN, onJump}: DateJumperProps): JSX.Element {
+    const {todayYear, todayMonth, todayDay, startYear, endYear} = React.useMemo(() => {
+        const [todayYear, todayMonth, todayDay] = jdnGregorian(todayJDN);
+        const [startYear] = jdnGregorian(minJDN);
+        const [endYear] = jdnGregorian(maxJDN);
+        return {todayYear, todayMonth, todayDay, startYear, endYear};
+    }, [minJDN, maxJDN, todayJDN]);
+
+    const [year, setYear] = React.useState(todayYear.toString());
+    const [month, setMonth] = React.useState(todayMonth.toString());
+    const [day, setDay] = React.useState(todayDay.toString());
+
+    const validYear = /^-?\d+$/.test(year) && startYear <= +year && +year <= endYear;
+    const validMonth = /^\d+$/.test(month) && 1 <= +month && +month <= 12;
+    const validDay = /^\d+$/.test(day) && 1 <= +day && +day <= 31;
+
+    function goToGregorian(event: React.FormEvent) {
+        event.preventDefault();
+
+        if (!validYear || !validMonth || !validDay)
+            return;
+
+        onJump(gregorianJDN(+year, +month, +day));
+    }
+
+    return <form className="input-group" onSubmit={goToGregorian}>
+        <span className="input-group-text">Gregorian<span className="hide-small">&nbsp;Date</span></span>
+        <input type="number" className={`form-control go-year ${validYear ? '' : 'is-invalid'}`}
+               onChange={e => setYear(e.target.value)} value={year}
+               min={startYear} max={endYear}/>
+        <input type="number" className={`form-control go-month ${validMonth ? '' : 'is-invalid'}`}
+               onChange={e => setMonth(e.target.value)} value={month}
+               min={1} max={12}/>
+        <input type="number" className={`form-control go-day ${validDay ? '' : 'is-invalid'}`}
+               onChange={e => setDay(e.target.value)} value={day}
+               min={1} max={31}/>
+        <button type="submit" className="form-control btn btn-primary go-button">Go</button>
+    </form>;
+}
diff --git a/common/src/dateJump/base.ts b/common/src/dateJump/base.ts
new file mode 100644
index 0000000..958516f
--- /dev/null
+++ b/common/src/dateJump/base.ts
@@ -0,0 +1,6 @@
+export type DateJumperProps = {
+    minJDN: number;
+    maxJDN: number;
+    todayJDN: number;
+    onJump: (jdn: number) => void;
+};
\ No newline at end of file
diff --git a/common/src/dateJump/index.ts b/common/src/dateJump/index.ts
new file mode 100644
index 0000000..feb9e73
--- /dev/null
+++ b/common/src/dateJump/index.ts
@@ -0,0 +1,3 @@
+import GregorianJumper from './GregorianJumper';
+
+export {GregorianJumper};
diff --git a/common/src/french/index.ts b/common/src/french/index.ts
index 3061f5d..023dd3b 100644
--- a/common/src/french/index.ts
+++ b/common/src/french/index.ts
@@ -1,6 +1,5 @@
 import data from './cal.json';
 import ruralName from './rural-days.json';
-import {jdnGregorian} from '../gregorian';
 
 // Month 13 is for the complementary days
 export type FrenchMonth = 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13;
@@ -145,9 +144,6 @@ export function dateRuralName(month: FrenchMonth, day: FrenchDay): { name: strin
     return {name, title};
 }
 
-export const startGregorian = jdnGregorian(frStartJD);
-export const endGregorian = jdnGregorian(frEndJD);
-
 export function frDateFormat({year, month, day}: { year: number, month: FrenchMonth, day: FrenchDay }): string {
     return `${dateName(month, day)} ${year}`;
 }
diff --git a/frcal/src/App.tsx b/frcal/src/App.tsx
index f863885..e833e7c 100644
--- a/frcal/src/App.tsx
+++ b/frcal/src/App.tsx
@@ -1,16 +1,9 @@
-import React, {FormEvent} from 'react';
+import React from 'react';
 import {Calendar} from './Calendar';
-import {
-    endGregorian,
-    frEndJD,
-    FrenchMonth,
-    frSupportedYear,
-    jdnFrench,
-    startGregorian,
-    frStartJD,
-} from '@common/french';
-import {dateJDN, gregorianJDN} from '@common/gregorian';
+import {FrenchMonth, frEndJD, frStartJD, frSupportedYear, jdnFrench} from '@common/french';
+import {dateJDN} from '@common/gregorian';
 import {TimeOfDay} from './TimeOfDay';
+import {GregorianJumper} from '@common/dateJump';
 
 type YearMonth = {
     year: number;
@@ -31,9 +24,6 @@ function parseURL(): YearMonth | null {
 
 type AppState = YearMonth & {
     todayJDN: number,
-    goYear: string,
-    goMonth: string,
-    goDay: string,
 };
 
 class App extends React.Component<{}, AppState> {
@@ -41,16 +31,12 @@ class App extends React.Component<{}, AppState> {
 
     constructor(props: {}) {
         super(props);
-        const today = new Date();
-        const todayJDN = dateJDN(today);
+        const todayJDN = dateJDN(new Date());
         const {year, month} = jdnFrench(todayJDN);
 
         this.state = {
             ...(parseURL() || {year, month}),
             todayJDN,
-            goYear: today.getFullYear().toString(),
-            goMonth: (today.getMonth() + 1).toString(),
-            goDay: today.getDate().toString(),
         };
         this.updateStateFromURL = this.updateStateFromURL.bind(this);
     }
@@ -75,38 +61,10 @@ class App extends React.Component<{}, AppState> {
         }
     }
 
-    changeField(field: keyof AppState, event: any) {
-        this.setState({[field]: event.target.value});
-    }
-
-    validYear() {
-        return /^-?\d+$/.test(this.state.goYear) && startGregorian[0] <= +this.state.goYear &&
-            +this.state.goYear <= endGregorian[0];
-    }
-
-    validMonth() {
-        return /^\d+$/.test(this.state.goMonth) && 1 <= +this.state.goMonth && +this.state.goMonth <= 12;
-    }
-
-    validDay() {
-        return /^\d+$/.test(this.state.goDay) && 1 <= +this.state.goDay && +this.state.goDay <= 31;
-    }
-
-    goToGregorian(event: FormEvent) {
-        event.preventDefault();
-
-        if (!this.validYear() || !this.validMonth() || !this.validDay())
-            return;
-
-        const jdn = gregorianJDN(+this.state.goYear, +this.state.goMonth, +this.state.goDay);
-        const {year, month} = jdnFrench(Math.min(Math.max(frStartJD, jdn), frEndJD));
-        this.setState({year, month});
-    }
-
     setState(state: any, callback?: () => void) {
         super.setState(state, () => {
             this.updateURL();
-            callback && callback();
+            callback?.();
         });
     }
 
@@ -114,6 +72,11 @@ class App extends React.Component<{}, AppState> {
         this.setState({todayJDN});
     };
 
+    goToJDN = (jdn: number) => {
+        const {year, month} = jdnFrench(Math.min(Math.max(frStartJD, jdn), frEndJD));
+        this.setState({year, month});
+    };
+
     render() {
         return <>
             <Calendar
@@ -126,19 +89,8 @@ class App extends React.Component<{}, AppState> {
 
             <div className="navigate">
                 <h4>Go to a date</h4>
-                <form className="input-group" onSubmit={this.goToGregorian.bind(this)}>
-                    <span className="input-group-text">Gregorian<span className="hide-small">&nbsp;Date</span></span>
-                    <input type="number" className={`form-control go-year ${this.validYear() ? '' : 'is-invalid'}`}
-                           onChange={this.changeField.bind(this, 'goYear')} value={this.state.goYear}
-                           min={startGregorian[0]} max={endGregorian[0]}/>
-                    <input type="number" className={`form-control go-month ${this.validMonth() ? '' : 'is-invalid'}`}
-                           onChange={this.changeField.bind(this, 'goMonth')} value={this.state.goMonth}
-                           min={1} max={12}/>
-                    <input type="number" className={`form-control go-day ${this.validDay() ? '' : 'is-invalid'}`}
-                           onChange={this.changeField.bind(this, 'goDay')} value={this.state.goDay}
-                           min={1} max={31}/>
-                    <button type="submit" className="form-control btn btn-primary go-button">Go</button>
-                </form>
+                <GregorianJumper minJDN={frStartJD} maxJDN={frEndJD} todayJDN={this.state.todayJDN}
+                                 onJump={this.goToJDN}/>
             </div>
         </>;
     }
diff --git a/jcal/src/App.tsx b/jcal/src/App.tsx
index 4515f49..9af34d5 100644
--- a/jcal/src/App.tsx
+++ b/jcal/src/App.tsx
@@ -1,13 +1,13 @@
-import React, {FormEvent} from 'react';
+import React from 'react';
 import {Calendar} from './Calendar';
-import {frEndJD, frStartJD} from '@common/french';
 import {dateJDN, gregorianJDN, JulianMonth} from '@common/gregorian';
 import {DayChanger} from '@common/DayChanger';
 import {jdnJulian} from '@common/julian';
+import {GregorianJumper} from '@common/dateJump';
 
 // Not real limitations other than JS number precision.
-const START_YEAR = -10_000_000_000_000;
-const END_YEAR = 10_000_000_000_000;
+const START_JDN = gregorianJDN(-10_000_000_000_000, 1, 1);
+const END_JDN = gregorianJDN(10_000_000_000_000, 12, 31);
 
 type YearMonth = {
     year: number;
@@ -28,9 +28,6 @@ function parseURL(): YearMonth | null {
 
 type AppState = YearMonth & {
     todayJDN: number,
-    goYear: string,
-    goMonth: string,
-    goDay: string,
 };
 
 class App extends React.Component<{}, AppState> {
@@ -38,16 +35,12 @@ class App extends React.Component<{}, AppState> {
 
     constructor(props: {}) {
         super(props);
-        const today = new Date();
-        const todayJDN = dateJDN(today);
+        const todayJDN = dateJDN(new Date());
         const [year, month] = jdnJulian(todayJDN);
 
         this.state = {
             ...(parseURL() || {year, month}),
             todayJDN,
-            goYear: today.getFullYear().toString(),
-            goMonth: (today.getMonth() + 1).toString(),
-            goDay: today.getDate().toString(),
         };
         this.updateStateFromURL = this.updateStateFromURL.bind(this);
     }
@@ -72,33 +65,6 @@ class App extends React.Component<{}, AppState> {
         }
     }
 
-    changeField(field: keyof AppState, event: any) {
-        this.setState({[field]: event.target.value});
-    }
-
-    validYear() {
-        return /^-?\d+$/.test(this.state.goYear) && START_YEAR <= +this.state.goYear && +this.state.goYear <= END_YEAR;
-    }
-
-    validMonth() {
-        return /^\d+$/.test(this.state.goMonth) && 1 <= +this.state.goMonth && +this.state.goMonth <= 12;
-    }
-
-    validDay() {
-        return /^\d+$/.test(this.state.goDay) && 1 <= +this.state.goDay && +this.state.goDay <= 31;
-    }
-
-    goToGregorian(event: FormEvent) {
-        event.preventDefault();
-
-        if (!this.validYear() || !this.validMonth() || !this.validDay())
-            return;
-
-        const jdn = gregorianJDN(+this.state.goYear, +this.state.goMonth, +this.state.goDay);
-        const [year, month] = jdnJulian(Math.min(Math.max(frStartJD, jdn), frEndJD));
-        this.setState({year, month});
-    }
-
     setState(state: any, callback?: () => void) {
         super.setState(state, () => {
             this.updateURL();
@@ -110,6 +76,11 @@ class App extends React.Component<{}, AppState> {
         this.setState({todayJDN});
     };
 
+    goToJDN = (jdn: number) => {
+        const [year, month] = jdnJulian(jdn);
+        this.setState({year, month});
+    };
+
     render() {
         return <>
             <Calendar
@@ -122,19 +93,8 @@ class App extends React.Component<{}, AppState> {
 
             <div className="navigate">
                 <h4>Go to a date</h4>
-                <form className="input-group" onSubmit={this.goToGregorian.bind(this)}>
-                    <span className="input-group-text">Gregorian<span className="hide-small">&nbsp;Date</span></span>
-                    <input type="number" className={`form-control go-year ${this.validYear() ? '' : 'is-invalid'}`}
-                           onChange={this.changeField.bind(this, 'goYear')} value={this.state.goYear}
-                           min={START_YEAR} max={END_YEAR}/>
-                    <input type="number" className={`form-control go-month ${this.validMonth() ? '' : 'is-invalid'}`}
-                           onChange={this.changeField.bind(this, 'goMonth')} value={this.state.goMonth}
-                           min={1} max={12}/>
-                    <input type="number" className={`form-control go-day ${this.validDay() ? '' : 'is-invalid'}`}
-                           onChange={this.changeField.bind(this, 'goDay')} value={this.state.goDay}
-                           min={1} max={31}/>
-                    <button type="submit" className="form-control btn btn-primary go-button">Go</button>
-                </form>
+                <GregorianJumper minJDN={START_JDN} maxJDN={END_JDN} todayJDN={this.state.todayJDN}
+                                 onJump={this.goToJDN}/>
             </div>
         </>;
     }