One source of time-zone rules
Conversions use a pinned copy of the IANA Time Zone Database, currently 2026e, through Moment Timezone. Server-rendered answers, tables, exports and the interactive converter use the same engine. Browser-native time-zone rules are not used for conversion results.
Fixed offsets and local civil time are different
EST means UTC−05:00 throughout the year. ET and New York follow the applicable local rules, including daylight saving time. Ambiguous abbreviations have an explicit default meaning and links to alternatives.
Dates matter
A local time can be skipped or repeated when clocks change. Skipped times are reported as unavailable. Repeated times show a choice between the first and second occurrence. Our supported conversion range is 2020–2040. Future dates follow currently published rules, which governments may change.
Working hours are preferences
The default is 09:00–17:00, Monday–Friday in each location. Change these settings to match your actual schedule. Holidays, leave and calendar availability are not included. Overnight work is assigned to the weekday on which the shift starts.
Meeting recommendations
We evaluate candidate starts every 15 minutes and check every minute of the elapsed meeting duration. A recommendation fits only when the whole meeting is within both working windows. Otherwise, alternatives first minimize the greatest number of minutes outside one participant’s working window, then total outside minutes, then distance from the selected time. These are transparent scheduling preferences, not a measure of personal wellbeing.
Year-round working windows
We project each configured local working window into UTC separately between time-zone transitions, then intersect the two interval sets. This accounts for skipped and repeated hours, overnight shifts and different working weekdays. Annual summaries use source calendar dates whose weekday is selected for the host. Holidays and leave are not subtracted. Year-round start ranges are the intersection of valid 15-minute starts across every such date, for the full elapsed meeting duration. The upper bound is the last start, not the end of the meeting. The downloadable daily CSV includes the inputs and time-zone database version.
Annual charts and weekly meetings
Annual difference charts are computed from all published zone transitions, not sampled months. Chart boundaries are expressed in UTC. Weekly checks preserve the organizer’s local date and time. Calendar downloads create a single occurrence in UTC to avoid accidental recurrence assumptions.
City data
City coordinates, population-based catalog ordering and time-zone assignments are adapted from GeoNames, licensed under CC BY 4.0. We select records, normalize labels, preserve existing city URLs and join them to our time-zone engine. Population is not a search-volume estimate.
Content and updates
Explanations are generated from calculated facts. No language model computes offsets or meeting times. The catalog combines researched conversions and a wider city network. The expanded city pairs have not been individually verified for search demand; publication does not imply any prediction of traffic. New timezone data must pass regression tests before release.