About this tool
Compare a base time zone against up to four others and instantly see which hours of the day fall inside everyone's working hours. It is built for scheduling calls across regions, and it runs entirely in your browser — no time-zone database is bundled and nothing is sent anywhere.
For each hour 0–23 of a reference day in your base zone, the planner builds the matching instant and formats it in every selected zone using Intl.DateTimeFormat with hour12 false. Because it uses the browser's own Intl engine, the local hours are automatically correct for each zone's current UTC offset and daylight-saving rules. A column is highlighted when every selected zone's local hour falls within your chosen working window [start, end).
Pick a base zone, add one to four other zones, and set your working-hours start and end (default 9 to 17). The grid shows each zone's local hour per base-zone hour, highlights the fully-overlapping columns, and lists the best meeting hours in base-zone time below it.