Solstice

Solstice is a free, open-source time zone converter that runs entirely in your browser. Nothing to install, no account required, and no data is sent anywhere.

Technology

Built with plain HTML, CSS, and JavaScript. Uses the browser's built-in Intl.DateTimeFormat API for accurate time formatting and DST-aware UTC offset calculations. No frameworks, no external dependencies.

Coverage

59 cities across 6 regions: UTC, Americas, Europe, Africa, Asia, and Pacific.

Source

Open source on GitHub. Licensed under MIT.

Version

v1.0.0

Getting started

• Select a city from the + Add time zone dropdown to add a card.
• Hover a card and click the ✕ button to remove it.
• Drag cards left or right to reorder them.

Modes

• Now — live clock, updated every second across all zones.
• Plan a time — pick any date and time to compare across zones at once.
• Schedule — set a start time and duration. Cards show the full meeting window with amber highlights for unsociable hours.

Features

• Find Overlap — surfaces the best meeting times ranked by how convenient they are for everyone.
• Copy Schedule — copies all current zone times to your clipboard as plain text.
• Download Invite — generates a .ics calendar file ready to share. Available in Schedule mode.

Settings

• Click the gear icon at the top right to open the settings panel.
• Switch between 12-hour and 24-hour format, choose a theme, pick a color palette, set a default mode, and show or hide UTC offsets on each card.

Keyboard

• Press Escape to close any open panel or modal.