Time Zone Business Hours Overlap Calculator

Last reviewed: October 14, 2026

Find the hours when two cities are both within their working day. The chart marks the shared hours in green, and the summary under it lists them for Monday to Friday in the first city, in both cities' clock times.

Built for distributed teams, sales reps scheduling cross-border calls, freelancers working with international clients, and anyone who wants to answer the meeting-time question once and keep the link. The link reopens the same cities and hours and reads the offset again each time, so open it again after either city changes its clocks.

City A

City B

A start

A end

B start

B end

Show all 7 days (default Mon-Fri only)Offset: Manila is +12 h vs New York (ET)

New York (ET)	00	01	02	03	04	05	06	07	08	09	10	11	12	13	14	15	16	17	18	19	20	21	22	23
Mon
Tue
Wed
Thu
Fri

Both in business hours (overlap) A only B only

Weekday overlap summary (Mon-Fri)

No overlap on any weekday with these business hours. Consider extending one window or using async work patterns.

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Worked example: New York and Manila

New York and Manila are the default pair. Their offset is 12 hours while New York is on Eastern Daylight Time and 13 hours on Eastern Standard Time, and with both cities on 9am to 5pm there is no overlap at any time of year. Widen the windows to see where one appears: with New York on 9am to 8pm and Manila on 7am to 5pm, July gives one hour, 7pm to 8pm on Monday in New York against 7am to 8am on Tuesday in Manila, and January gives two, 6pm to 8pm against 7am to 9am. The summary prints that slot on all five rows, Monday to Friday in New York, and names Manila's day beside its time because it is not the row's: in July Monday's row reads "Manila Tue 07:00-08:00" and Friday's "Manila Sat 07:00-08:00". Friday evening in New York is Saturday morning in Manila, and the hour stays listed: the calculator names the day and does not judge whether anyone works on it.

What the chart does not do

The chart has one column for each hour of the first city and repeats one day's result on every row. It does not know either city's weekend or public holidays: the summary always lists Monday to Friday in the first city, and an hour it lists can fall on a Saturday or Sunday in the second, where the summary names that day beside the time. A window cannot run past midnight, so a night shift (22 to 6) shows no overlap. Mumbai is the one city in the list on a half-hour offset: with it the summary counts the half hour and gives the times to the minute, such as 13:30, and a column of the chart can be split between two colours.

Optimizing meeting times across multiple time zones

When no slot suits everyone, consider three options. Rotate the inconvenient slot so the same person is not always the one starting early or staying late. Keep live calls for decisions that need real-time discussion and move status updates to written or recorded form. Or split a large team into regional groups that meet inside their own time zones, with one cross-group handoff a week attended by a person from each group.

Asynchronous work alternatives when overlap is small

When the overlap is an hour or less, plan for most of the work to move without a live meeting. Put handoffs in writing and keep shared documents current, and give each side the authority to make routine decisions without waiting for an approval from a colleague whose working day has already ended. Agree in advance which decisions need the other side, and keep the overlap hour for those.

DST seasonal shifts

The calculator reads each city's offset from the time zone database in your browser at the moment you open the page, so daylight saving time is applied as that database records it for that day. Some pairs keep the same offset all year: Tokyo and Shanghai are 1 hour apart, as are Bangkok and Singapore, because none of the four changes its clocks. Others move. New York and London are 5 hours apart for most of 2026 and 4 hours apart from 8 to 29 March and from 25 October to 1 November, because the United States and the United Kingdom change their clocks on different Sundays; Los Angeles and Sydney range from 17 to 19 hours over the year. Not every change falls on a Sunday: in 2026 Cairo moves its clocks on Friday 24 April and on Thursday 29 October.

For informational purposes only

This calculator provides general estimates based on business day counting rules. It does not constitute legal advice. Deadlines in legal, regulatory, or contractual matters may be subject to jurisdiction-specific rules, court orders, or statutory exceptions. Always verify critical deadlines with a qualified professional.

Sources for these rules

Time Zone Database (tz): the history of local time, UTC offsets and daylight-saving rules for representative locations, updated as governments change them (Internet Assigned Numbers Authority (IANA))
Time Zone Database, release 2026e, file northamerica: Rule US from 2007, clocks forward on the second Sunday of March (Mar Sun>=8) and back on the first Sunday of November (Nov Sun>=1), at 2:00; the zones of New York and Los Angeles follow it (Internet Assigned Numbers Authority (IANA))
Time Zone Database, release 2026e, file asia: Asia/Tokyo at 9:00, Asia/Shanghai at 8:00, Asia/Bangkok at 7:00 and Asia/Singapore at 8:00, none under a rule that still changes its clocks (Japan's rules end in 1951, China's in 1991); Asia/Kolkata at 5:30 (Internet Assigned Numbers Authority (IANA))
Time Zone Database, release 2026e, file europe: Rule EU, clocks forward on the last Sunday of March and back on the last Sunday of October, at 1:00 UTC; Europe/London follows it (GMT/BST) (Internet Assigned Numbers Authority (IANA))
Time Zone Database, release 2026e, file africa: Rule Egypt from 2023, clocks forward on the last Friday of April at 0:00 and back on the last Thursday of October at 24:00 (Internet Assigned Numbers Authority (IANA))
Time Zone Database, release 2026e, file australasia: Rule AN from 2008 (New South Wales), clocks back on the first Sunday of April and forward on the first Sunday of October; Australia/Sydney follows it (Internet Assigned Numbers Authority (IANA))

Checked October 14, 2026. All sources

Frequently Asked Questions

How does the calculator account for daylight saving time?

The chart applies one offset between the two cities, the one in force when you open the page, to every row. In a week in which one city changes its clocks and the other does not, the rows after the change are an hour out until you reload the page after it. New York and London show this twice a year: in 2026 their offset is 4 hours rather than 5 from 8 to 29 March and from 25 October to 1 November.

Why does the table show some hours with B in the next day?

The hover text gives B's local time for each cell and puts B's day before it when B's calendar day is not A's, and the summary under the chart does the same for the hours it lists. At 9pm on a Monday in New York, for example, it is already 9am on Tuesday in Manila while New York is on daylight time, and 10am in winter, so in summer the hover text on Monday's row reads "Manila: Tue 09:00". The calculator wraps B's hour past midnight when it looks for overlap and lists the hour whichever day that is in B, a Saturday or Sunday included. It names the day so that a meeting is not booked on the wrong day for one party.

What if there is no overlap at all?

Some pairs have none with 9am to 5pm on both sides, among them Buenos Aires and Sydney, and New York and Manila. The calculator says so in the summary. To find a slot, widen the windows and watch the chart: the worked example above adds three hours to New York's day and two to Manila's before an hour appears, and for either pair, widening one side alone by one or two hours gives none on any day of 2026. Or move the exchange to written handoffs that do not need both sides at once.

Can I add a third or fourth city?

Not in this calculator: the chart compares two cities. For three or more, run the pairs (A with B, A with C, B with C) and look for the hours that appear in every result. A larger team can also pick two anchor cities and have everyone else align with one of them rather than searching for a window that suits all.

Why use this rather than a world-clock tool?

A world clock shows the time in several places at once. This calculator answers a narrower question, when both of you are within your working hours, and shows it as a block in the chart plus a Monday-to-Friday summary. Once you change a city or an hour, the page address carries both cities and both windows, so the link reopens them for whoever follows it. The chart they see uses the offset of the day they open it.