How do I find overlapping business hours between two time zones?

Convert both workday windows to UTC, then find the intersection. For example, New York (UTC−5) working 9 AM–5 PM spans 14:00–22:00 UTC. London (UTC+0) working 9 AM–5 PM spans 9:00–17:00 UTC. Overlap: 14:00–17:00 UTC = 3 hours (9 AM–12 PM New York, 2 PM–5 PM London).

What UTC offset should I use for my time zone?

Common offsets: Los Angeles / PST = UTC−8 (PDT = UTC−7), Denver / MST = UTC−7, Chicago / CST = UTC−6, New York / EST = UTC−5 (EDT = UTC−4), London / GMT = UTC+0 (BST = UTC+1), Paris / CET = UTC+1 (CEST = UTC+2), Dubai = UTC+4, India / IST = UTC+5.5, China / CST = UTC+8, Japan / JST = UTC+9, Sydney / AEST = UTC+10.

What if there is no overlap at all?

When workday windows don't overlap, the calculator also checks extended hours (8 AM–8 PM). If even those don't overlap, someone needs to schedule outside normal hours. In those cases, rotate who takes the inconvenient slot — alternating early mornings and late evenings is fairer than one side always bearing the cost.

How does daylight saving time affect this?

Daylight saving time shifts UTC offsets by 1 hour for the regions that observe it, and the transitions happen on different dates in different countries. Always confirm the current UTC offset for both locations on the date of the meeting, since the two locations may be in or out of DST at different times.

Meeting Time Planner

Find the best times to call or meet across two different time zones.

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What This Calculator Does

Find the window when both you and someone in another time zone are simultaneously in working hours. Enter your UTC offsets and workday window to see the overlap, the best meeting times in both zones, and the time zone difference.

It combines Your UTC Offset (hours), Their UTC Offset (hours), Workday Start (24h), Workday End (24h) to estimate Business Hours Overlap, Overlap — Your Time (UTC−5), Overlap — Their Time (UTC+1).

Formula & Method

Overlap is computed by converting both workday windows to UTC and finding their intersection:

t_{\text{start, UTC}} = t_{\text{workday start}} - \text{UTC offset}

Overlap window:

[\max(\text{starts}_{\text{UTC}}),\ \min(\text{ends}_{\text{UTC}})]

Convert back to local times by adding each location's UTC offset to the UTC overlap bounds.

Notation used in the formulas: $R$ = Business Hours Overlap; $x_{1}$ = Your UTC Offset (hours); $x_{2}$ = Their UTC Offset (hours); $x_{3}$ = Workday Start (24h); $x_{4}$ = Workday End (24h).

Method summary: inputs are normalized to consistent units, core equations are evaluated, then secondary values are derived and rounded for display.

Use this when scheduling calls with colleagues, clients, or family across time zones. Enter your UTC offset and theirs, set your workday hours, and see exactly when both of you are simultaneously available — no mental math required.

Worked Examples

New York (UTC−5) calling London (UTC+0), standard 9–5

New York workday in UTC: 9 − (−5) = 14:00 to 17 − (−5) = 22:00 London workday in UTC: 9 − 0 = 09:00 to 17 − 0 = 17:00 Overlap in UTC: max(14, 9) = 14:00 to min(22, 17) = 17:00 Overlap duration: 3 hours Overlap in New York time: 14:00 + (−5) = 9:00 AM to 12:00 PM Overlap in London time: 14:00 + 0 = 2:00 PM to 5:00 PM Best meeting time: 10:00 AM New York / 3:00 PM London

San Francisco (UTC−8) calling Tokyo (UTC+9), 9–5

SF workday in UTC: 9 − (−8) = 17:00 to 17 − (−8) = 25:00 (wraps to 01:00 next day) Tokyo workday in UTC: 9 − 9 = 00:00 to 17 − 9 = 8:00 Overlap in UTC: max(17, 0) = 17:00 to min(25, 8) = 8:00 → no overlap in standard hours Extended hours (8 AM – 8 PM) check: SF extended in UTC: 8 − (−8) = 16:00 to 20 − (−8) = 28:00 Tokyo extended in UTC: 8 − 9 = −1:00 (= 23:00 prev) to 20 − 9 = 11:00 No overlap even with extended hours for this 17-hour gap. Recommendation: Rotate the burden — SF takes an early 7 AM call (4 PM Tokyo) or Tokyo stays until 6 PM (9 AM SF next day).

Common Mistakes

Using city names instead of UTC offsets — remember that DST shifts offsets by 1 hour for about half the year in many regions (e.g., New York is UTC−5 in winter, UTC−4 in summer).
Assuming the other person uses the same workday hours as you — the calculator defaults to 9 AM–5 PM for both; adjust if their culture has different norms.
Forgetting that India (UTC+5:30) and Nepal (UTC+5:45) use half- and quarter-hour offsets — use the 0.5 step and enter 5.5 for IST.

Frequently Asked Questions

How do I find overlapping business hours between two time zones?: Convert both workday windows to UTC, then find the intersection. For example, New York (UTC−5) working 9 AM–5 PM spans 14:00–22:00 UTC. London (UTC+0) working 9 AM–5 PM spans 9:00–17:00 UTC. Overlap: 14:00–17:00 UTC = 3 hours (9 AM–12 PM New York, 2 PM–5 PM London).
What UTC offset should I use for my time zone?: Common offsets: Los Angeles / PST = UTC−8 (PDT = UTC−7), Denver / MST = UTC−7, Chicago / CST = UTC−6, New York / EST = UTC−5 (EDT = UTC−4), London / GMT = UTC+0 (BST = UTC+1), Paris / CET = UTC+1 (CEST = UTC+2), Dubai = UTC+4, India / IST = UTC+5.5, China / CST = UTC+8, Japan / JST = UTC+9, Sydney / AEST = UTC+10.
What if there is no overlap at all?: When workday windows don't overlap, the calculator also checks extended hours (8 AM–8 PM). If even those don't overlap, someone needs to schedule outside normal hours. In those cases, rotate who takes the inconvenient slot — alternating early mornings and late evenings is fairer than one side always bearing the cost.
How does daylight saving time affect this?: Daylight saving time shifts UTC offsets by 1 hour for the regions that observe it, and the transitions happen on different dates in different countries. Always confirm the current UTC offset for both locations on the date of the meeting, since the two locations may be in or out of DST at different times.

Inputs Used

Your UTC Offset (hours): Your UTC offset. E.g. −5 for EST, −8 for PST, 0 for GMT, +1 for CET, +5.5 for IST, +9 for JST.
Their UTC Offset (hours): Their UTC offset. E.g. −5 for EST, −8 for PST, 0 for GMT, +1 for CET, +5.5 for IST, +9 for JST.
Workday Start (24h): Start of the workday in local time (24h). 9 = 9:00 AM, 8.5 = 8:30 AM.
Workday End (24h): End of the workday in local time (24h). 17 = 5:00 PM, 18.5 = 6:30 PM.

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