Every city on one 24-hour grid, lined up on the same instant. Tap an hour to pick a meeting slot and send it to any calendar. Free, no account, as many rows as you need.
Each row is a time zone and each column is the same instant, so the numbers you read down a column are one moment of the day worn by different clocks. The shading marks the working day, the evening and the night in every zone, which is what actually decides whether a meeting time is reasonable. Your own zone comes first, read from the browser, and the Zulu row stays on the board because UTC is the reference everything else is measured against.
Add rows by city name, country, zone abbreviation or IANA id, reorder them, and mark any row as home - the grid re-anchors on its day and the other rows show their offset against it. Tapping an hour selects a one-hour slot across every row, and dragging its edges stretches it in whole-hour steps. Once a slot is picked, the left side of each row shows its start and end in that zone, and the bar above the grid copies the times as text, downloads an iCal file for Outlook and Apple Calendar, or opens a prefilled Google Calendar event. The date strip above switches between the next seven days, with weekends set apart.
The set of rows and the selected slot are saved in your browser and mirrored into the page address, so copying the URL from the address bar hands the exact same board to a colleague. Daylight saving needs no attention here: every cell is computed from the zone database, on transition days the skipped or repeated hour simply shows up in the row.
If one of the sides is written with a Z on the end, the dedicated pages go deeper: the Zulu time converter renders one Zulu time in every common format, and the Zulu pair pages cover single zones like Zulu to EST or Zulu to CET with full hour charts and the daylight saving rules. The four-digit notation itself is explained on the military time converter.