diff --git a/src/__tests__/BerlinClock.test.tsx b/src/__tests__/BerlinClock.test.tsx
new file mode 100644
index 0000000..7a18e9d
--- /dev/null
+++ b/src/__tests__/BerlinClock.test.tsx
@@ -0,0 +1,11 @@
+import { render } from '@testing-library/react';
+import { BerlinClock } from '../containers/BerlinClock';
+
+describe('BerlinClock', () => {
+  it('renders when enabled', () => {
+    render(<BerlinClock enabled={true} />);
+  });
+  it('does not render when disabled', () => {
+    render(<BerlinClock enabled={false} />);
+  });
+});
diff --git a/src/__tests__/DigitalClock.test.tsx b/src/__tests__/DigitalClock.test.tsx
new file mode 100644
index 0000000..0381d1e
--- /dev/null
+++ b/src/__tests__/DigitalClock.test.tsx
@@ -0,0 +1,8 @@
+import { render } from '@testing-library/react';
+import { DigitalClock } from '../containers/DigitalClock';
+
+describe('DigitalClock', () => {
+  it('renders when enabled', () => {
+    render(<DigitalClock enabled={true} />);
+  });
+});
diff --git a/src/__tests__/Lamp.test.tsx b/src/__tests__/Lamp.test.tsx
new file mode 100644
index 0000000..6b71f95
--- /dev/null
+++ b/src/__tests__/Lamp.test.tsx
@@ -0,0 +1,9 @@
+import { render, screen } from '@testing-library/react';
+import { Lamp } from '../components/Lamp';
+import { LampState } from '../types';
+
+describe('Lamp', () => {
+  it('renders without crashing', () => {
+    render(<Lamp state={LampState.Y} />);
+  });
+});
diff --git a/src/__tests__/LampLine.test.tsx b/src/__tests__/LampLine.test.tsx
new file mode 100644
index 0000000..45f0f37
--- /dev/null
+++ b/src/__tests__/LampLine.test.tsx
@@ -0,0 +1,11 @@
+import { render } from '@testing-library/react';
+import { LampLine } from '../components/LampLine';
+import { LampState } from '../types';
+
+describe('LampLine', () => {
+  it('renders correct number of lamps', () => {
+    const states = [LampState.Y, LampState.R, LampState.O];
+    render(<LampLine states={states} />);
+    // TODO: assert number of child lamps
+  });
+});
diff --git a/src/__tests__/TimeConverter.test.tsx b/src/__tests__/TimeConverter.test.tsx
new file mode 100644
index 0000000..cf4c3de
--- /dev/null
+++ b/src/__tests__/TimeConverter.test.tsx
@@ -0,0 +1,13 @@
+import { render, screen, fireEvent } from '@testing-library/react';
+import { TimeConverter } from '../containers/TimeConverter';
+
+describe('TimeConverter', () => {
+  it('renders the toggle checkbox', () => {
+    render(<TimeConverter />);
+    expect(screen.getByRole('checkbox')).toBeInTheDocument();
+  });
+  it('disables clocks when checkbox is checked', () => {
+    render(<TimeConverter />);
+    // TODO
+  });
+});
diff --git a/src/__tests__/types.test.ts b/src/__tests__/types.test.ts
new file mode 100644
index 0000000..5497cae
--- /dev/null
+++ b/src/__tests__/types.test.ts
@@ -0,0 +1,10 @@
+import { LampState, BerlinClock } from '../types';
+
+describe('Types', () => {
+  it('LampState has correct values', () => {
+    expect(LampState.Y).toBe('Y');
+    expect(LampState.R).toBe('R');
+    expect(LampState.O).toBe('O');
+    expect(LampState.N).toBe('N');
+  });
+});
diff --git a/src/__tests__/useCurrentTime.test.ts b/src/__tests__/useCurrentTime.test.ts
new file mode 100644
index 0000000..5348220
--- /dev/null
+++ b/src/__tests__/useCurrentTime.test.ts
@@ -0,0 +1,10 @@
+import { renderHook, act } from '@testing-library/react';
+import { useCurrentTime } from '../hooks/useCurrentTime';
+
+describe('useCurrentTime', () => {
+  it('returns a date and setter', () => {
+    const { result } = renderHook(() => useCurrentTime());
+    expect(result.current.currentTime).toBeInstanceOf(Date);
+    expect(typeof result.current.setCurrentTime).toBe('function');
+  });
+});
diff --git a/src/__tests__/utils.test.ts b/src/__tests__/utils.test.ts
new file mode 100644
index 0000000..02562c3
--- /dev/null
+++ b/src/__tests__/utils.test.ts
@@ -0,0 +1,16 @@
+import { dateToDigital, digitalToDate, dateToBerlin, berlinToDate } from '../utils';
+
+describe('Utils', () => {
+  it('dateToDigital returns correct format', () => {
+    // TODO
+  });
+  it('digitalToDate returns a Date', () => {
+    // TODO
+  });
+  it('dateToBerlin returns a BerlinClock', () => {
+    // TODO
+  });
+  it('berlinToDate returns a Date', () => {
+    // TODO
+  });
+});
diff --git a/src/components/Lamp.tsx b/src/components/Lamp.tsx
new file mode 100644
index 0000000..286dfeb
--- /dev/null
+++ b/src/components/Lamp.tsx
@@ -0,0 +1,9 @@
+import { LampState } from '../types';
+
+interface LampProps {
+  state: LampState;
+}
+
+export function Lamp({ state }: LampProps) {
+  return null;
+}
diff --git a/src/components/LampLine.tsx b/src/components/LampLine.tsx
new file mode 100644
index 0000000..4826284
--- /dev/null
+++ b/src/components/LampLine.tsx
@@ -0,0 +1,9 @@
+import { LampState } from '../types';
+
+interface LampLineProps {
+  states: LampState[];
+}
+
+export function LampLine({ states }: LampLineProps) {
+  return null;
+}
diff --git a/src/containers/BerlinClock.tsx b/src/containers/BerlinClock.tsx
new file mode 100644
index 0000000..1894707
--- /dev/null
+++ b/src/containers/BerlinClock.tsx
@@ -0,0 +1,15 @@
+import { useState } from 'react';
+import { LampLine } from '../components/LampLine';
+import { useCurrentTime } from '../hooks/useCurrentTime';
+import { dateToBerlin } from '../utils';
+
+interface BerlinClockProps {
+  enabled: boolean;
+}
+
+export function BerlinClock({ enabled }: BerlinClockProps) {
+  const { currentTime } = useCurrentTime();
+  const berlin = dateToBerlin(currentTime);
+  // Will render four LampLine components
+  return null;
+}
diff --git a/src/containers/DigitalClock.tsx b/src/containers/DigitalClock.tsx
new file mode 100644
index 0000000..4408719
--- /dev/null
+++ b/src/containers/DigitalClock.tsx
@@ -0,0 +1,13 @@
+import { useState } from 'react';
+import { useCurrentTime } from '../hooks/useCurrentTime';
+import { dateToDigital } from '../utils';
+
+interface DigitalClockProps {
+  enabled: boolean;
+}
+
+export function DigitalClock({ enabled }: DigitalClockProps) {
+  const { currentTime } = useCurrentTime();
+  const digital = dateToDigital(currentTime);
+  return null;
+}
diff --git a/src/containers/TimeConverter.tsx b/src/containers/TimeConverter.tsx
new file mode 100644
index 0000000..9e35a2e
--- /dev/null
+++ b/src/containers/TimeConverter.tsx
@@ -0,0 +1,10 @@
+import { useState } from 'react';
+import { BerlinClock } from './BerlinClock';
+import { DigitalClock } from './DigitalClock';
+import { useCurrentTime } from '../hooks/useCurrentTime';
+
+export function TimeConverter() {
+  const [useSystemTime, setUseSystemTime] = useState(false);
+  // When useSystemTime is true, both BerlinClock and DigitalClock are disabled.
+  return null;
+}
diff --git a/src/hooks/useCurrentTime.ts b/src/hooks/useCurrentTime.ts
new file mode 100644
index 0000000..da9055d
--- /dev/null
+++ b/src/hooks/useCurrentTime.ts
@@ -0,0 +1,9 @@
+import { useState } from 'react';
+
+export function useCurrentTime(): {
+  currentTime: Date;
+  setCurrentTime: React.Dispatch<React.SetStateAction<Date>>;
+} {
+  const [currentTime, setCurrentTime] = useState(new Date());
+  return { currentTime, setCurrentTime };
+}
diff --git a/src/types/index.ts b/src/types/index.ts
new file mode 100644
index 0000000..8ec6dc0
--- /dev/null
+++ b/src/types/index.ts
@@ -0,0 +1,14 @@
+export enum LampState {
+  Y = 'Y',   // Yellow
+  R = 'R',   // Red
+  O = 'O',   // Off
+  N = 'N',   // None / undefined
+}
+
+export interface BerlinClock {
+  secondsRow: LampState[];
+  fiveHours: LampState[];
+  oneHour: LampState[];
+  fiveMinutes: LampState[];
+  oneMinute: LampState[];
+}
diff --git a/src/utils/index.ts b/src/utils/index.ts
new file mode 100644
index 0000000..a864c13
--- /dev/null
+++ b/src/utils/index.ts
@@ -0,0 +1,25 @@
+import { BerlinClock } from '../types';
+
+export function dateToDigital(date: Date): string {
+  // returns "HH:mm:ss"
+  return '';
+}
+
+export function digitalToDate(digital: string): Date {
+  // parses "HH:mm:ss"
+  return new Date();
+}
+
+export function dateToBerlin(date: Date): BerlinClock {
+  return {
+    secondsRow: [],
+    fiveHours: [],
+    oneHour: [],
+    fiveMinutes: [],
+    oneMinute: [],
+  };
+}
+
+export function berlinToDate(berlin: BerlinClock): Date {
+  return new Date();
+}