Find what time it is elsewhere when scheduling international calls and travel.
Overview
Global coordination requires converting local times to other zones. Offsets from UTC (Coordinated Universal Time) shift hours forward or backward, with possible date changes when crossing the international date line.
Target time = source time + (UTC_target − UTC_source), adjusting day when hours go below 0 or above 24. Daylight saving time (DST) shifts offsets seasonally; use the correct offset for the specific calendar date.
Abbreviations like EST and IST are ambiguous without dates and regions. Prefer IANA zone names (America/New_York) when accuracy matters because political offset changes occur.
Meetings spanning zones benefit from listing both UTC and local times in invites to avoid ambiguous “tomorrow morning” phrasing.
Steps
Date and time in origin zone.
Pick offset or named zone.
Destination offset or zone.
Use date-specific rules when available.
Shift hours and adjust date.
Document both zones for attendees.
Math
T_target = T_source + (UTC_target − UTC_source)
Hour difference applied to clock time with day rollover when result crosses midnight.
Worked cases
Difference +4:30
14:30 target time.
Large negative shift may move to Monday
Check previous calendar day.
Display in New York and Tokyo zones
Different local clocks, same moment.
Why use this
Questions