Time Zone Business Hours Overlap Calculator

Find the hours when two cities are both within their working day. The chart highlights overlap windows in green and the per-weekday summary tells you exactly when to book a meeting that does not require either party to log in early or stay late.

Built for distributed teams, sales reps scheduling cross-border calls, freelancers working with international clients, and anyone trying to answer the meeting-time question once, save the link, and stop recalculating it every Monday.

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Worked example: New York and Manila

Pre-loaded as the default. New York to Manila is a 12 or 13 hour offset depending on US DST state. With both windows set to 9am-5pm, the overlap is essentially nil during US Eastern Daylight Time. Extending New York to 7am-7pm or Manila to 7am-9pm pulls one hour of overlap into the workday: 7am-8am Manila Tuesday morning aligns with 7pm-8pm Monday evening in New York. Most outsourcing arrangements with the Philippines work this way: a daily 30-minute handoff call where Manila wraps up its day and New York opens.

Optimizing meeting times across multiple time zones

Three practical patterns for distributed teams. First, the rotating penalty: if no time works for everyone, rotate the painful slot week by week so the same person is not always the one logging in at 6am. Second, the asynchronous default: record a weekly Loom or Zoom video summary instead of a live all-hands; reserve live calls for decisions that genuinely require real-time discussion. Third, the regional anchor: split the team into 2 or 3 regional pods (Americas, EMEA, APAC) with a daily intra-pod standup and a weekly cross-pod handoff where only one rep from each pod attends.

Asynchronous work alternatives when overlap is small

When overlap is one hour or less, live meetings stop being the primary collaboration mechanism. The teams that succeed in this regime invest in shared documents (Notion, Confluence, Coda), long-form async chat (threaded Slack with strict thread etiquette), and recorded async video (Loom for status updates, Tella for tutorials). The decision-rights matrix matters more here: a designer in Manila needs explicit autonomy to ship a change without waiting for an Eastern-time approval that will not arrive for 14 hours. Companies that get this right pay 30 to 50 percent of their payroll across non-overlapping zones; companies that do not end up forcing one zone to keep the other on call.

DST seasonal shifts

Some pairs of cities have stable year-round offsets (Tokyo and Beijing are always 1 hour apart; Bangkok and Singapore are always 1 hour apart). Others swing 1 or 2 hours seasonally because one or both observe DST. The Sydney-San Francisco pair shifts most dramatically: Sydney goes off DST in April when SF is still on DST, and SF goes off DST in November when Sydney is back on. The offset varies between 17 and 19 hours over the year. Bookmark the calculator and check it each spring and fall to update meeting times that you set during the previous season.

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.

Frequently Asked Questions

How does the calculator account for daylight saving time?

The chart uses one offset between the two zones, computed at page load from the current date. So if you load the page when New York is on Eastern Daylight Time and London is on British Summer Time, you see the EDT/BST offset (5 hours). The same offset is applied to all 7 weekday rows, which is accurate within a week because DST transitions always happen on a Sunday: a mid-week jump cannot land inside the displayed week. When the US falls back in November and the UK falls back the previous Sunday, the offset briefly drops to 4 hours, then returns to 5. Bookmark the calculator and revisit it after each transition; the chart will reflect the new offset on the next page load.

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

The hover tooltip shows when B's local clock has rolled into the next or previous day relative to A. A typical example: at 9pm Monday in New York, Manila is already 10am Tuesday. The calculator handles the day rollover internally so the overlap math stays correct, but the hover text surfaces it so you do not accidentally schedule a meeting that lands on the wrong day for one party.

What if there is no overlap at all?

Some pairs (Honolulu and Tokyo, or Buenos Aires and Sydney) have zero overlap with default 9-5 windows. The calculator reports this explicitly. The practical workarounds are: extend one party's window by an hour or two, schedule weekly handoff calls on Monday or Friday rather than mid-week, or move to async-first work patterns where shared documents and recorded videos replace live meetings.

Can I add a third or fourth city?

Not in this calculator: the visual chart works best with two cities. For three or more, run pairwise comparisons (A vs B, A vs C, B vs C) and look for the intersection of intersections. For globally distributed teams, the practical approach is to nominate two anchor cities and have everyone else align to one of those rather than trying to find a window that works for all five.

Why use this rather than World Time Buddy or Every Time Zone?

Those tools are great for at-a-glance comparison. This calculator is purpose-built for the question "when are both of us actually open for business?" and shows the answer as a green block in the table plus a per-weekday textual summary. The shareable URL is also a clearer artifact to drop into a meeting invite or a Slack channel than a screenshot of a third-party site.