Working-Hours Overlap Calculator

Worked example

A 9 to 5 working window in America/New_York and a 9 to 5 working window in Europe/London on the same calendar date genuinely share a real overlap once both are converted onto a shared timeline, since New York's afternoon corresponds to London's evening, both still inside each side's own stated working hours. Narrow the New York window to end at noon instead of 5 PM, and the overlap shrinks to whatever portion of London's morning still falls within that shorter New York afternoon, or disappears entirely if the two windows no longer touch at all once converted. The raw clock numbers on each side never directly tell you the answer. Only converting both through their own real zones and comparing the result on one shared timeline does.

Common mistakes

• Comparing local clock hours directly without converting each one to a real instant first. Two windows that both read 9 to 5 in their own zones do not overlap the way the bare numbers might suggest.
• Assuming more participants always means a smaller overlap. That is usually true, but the actual result depends on exactly where each participant's working hours fall, not just how many people are involved.

Limitations

This checks one specific date per participant. To scan across a range of dates instead of a single day, use the Time Zone Availability Planner, which is built specifically for that broader search.