US time zone guides

Each guide explains one rule behind the live US time zone map and links to the tool that applies it. They are short on purpose: the answer is in the first paragraph, and every number is either computed by the site’s tools or cited.

• Scheduling meetings across US time zones

  The working hours each zone combination shares, for summer and winter.

  Tool: Meeting planner

• EST vs EDT: US time zone abbreviations

  Which abbreviation and UTC offset each zone uses today, and when it switches.

  Tool: Time converter

• How US time zone boundaries are set

  Who draws the lines, how a county changes zones, and why maps disagree.

  Tool: Live US map

More on the rules

Daylight saving time has its own map, which shows the places that switch and the two states that don’t: see the daylight saving time map. Split states, where a line runs through the state, each have a page in thestate time zone maps, from Florida’s Panhandle to the Indiana counties near Chicago. For 24-hour times on schedules and timetables, themilitary time chart converts both ways.

If a guide gets something wrong, or a boundary has changed, thecontact page explains how to send a correction. Corrections are checked against the federal regulations and the IANA time zone database before the site is updated, and the date at the top of each guide shows when it last changed.