Timezone Overlap Tool

Time zone overlap is the portion of the day when people in different timezones are simultaneously within their working hours. For example, if New York (9 AM–5 PM) and London (9 AM–5 PM) overlap from 9 AM–12 PM ET (2 PM–5 PM BST), that shared window is the overlap. The more overlap, the easier it is to schedule meetings.

Nepal Standard Time uses UTC+5:45, one of several non-whole-hour timezone offsets in the world. Nepal chose this offset to align its daylight hours with the country's geography, specifically so that solar noon falls near the center of the country. Other examples of non-hour offsets include Newfoundland (UTC-3:30), India (UTC+5:30), and parts of Australia (UTC+9:30).

Both smartphones and computers support displaying multiple clocks. On iPhone, add World Clock widgets. On Android, use the Clock app to add city widgets. On Windows, add multiple clocks in the taskbar settings. On macOS, add world clocks in the widget panel. Many people also use browser-based timezone tools for quick comparisons during work.

The tz database (also called the IANA Time Zone Database) is the authoritative dataset used by computers and operating systems worldwide to track timezone names, UTC offsets, and daylight saving time rules. It assigns unique identifiers like America/New_York, Europe/London, and Asia/Kathmandu to each region, making timezone handling consistent across different software and platforms.

The world is conceptually divided into 24 hourly time zones, each 15 degrees of longitude wide, centered on the Prime Meridian (UTC+0). In reality, many regions use half-hour (UTC+5:30) or 45-minute (UTC+5:45) offsets, and some use daylight saving time, creating many more than 24 distinct zones. The IANA tz database lists over 500 unique timezone identifiers.

The '7 main time zones' usually refers to a simplified U.S.-centric grouping used for teaching: Atlantic, Eastern, Central, Mountain, Pacific, Alaska, and Hawaii-Aleutian. In the global context, there is no standard set of '7 main' time zones — the world has dozens of timezone offsets depending on geography, politics, and daylight saving policies.

Time overlap refers to the period when two or more schedules intersect. In the context of timezones, it usually means the shared window of working hours across different locations. For example, if Team A works 9–5 in New York and Team B works 9–5 in London, the overlap is the 3-hour window when both are simultaneously at work.

To convert between timezones, determine each timezone's UTC offset (including DST where applicable), then calculate the time difference. For example, New York (UTC-4 in summer) to London (UTC+1 in summer) is a 5-hour difference — when it's 9 AM in New York, it's 2 PM in London. A timezone overlap visualizer handles this automatically and shows you the shared availability across all timezones at once.

To convert a local time to UTC, subtract the timezone's UTC offset (including any daylight saving adjustment). For example, 2:00 PM in New York during EDT (UTC-4) is 6:00 PM UTC. During EST (UTC-5), 2:00 PM in New York is 7:00 PM UTC. Always confirm the current DST status because offsets change twice a year.

EST (Eastern Standard Time, UTC-5), CST (Central Standard Time, UTC-6), and MST (Mountain Standard Time, UTC-7) are North American timezone abbreviations. However, these abbreviations can be ambiguous — EST is also used in Australia, and CST is used in China (UTC+8). The IANA timezone identifiers like America/New_York or Australia/Sydney are more reliable for accurate scheduling.

7:30 AM to 4:30 PM is 9 hours. If a lunch break is included (typically 30–60 minutes), the actual working time is less. Many workplaces count 7.5 or 8 hours of actual work within a 9-hour window.

Remote teams rely on timezone overlaps to schedule meetings that fit everyone's working hours. By visualizing overlaps, teams can identify the best daily windows for standups, client calls, and collaborative work. Teams with little overlap often rotate meeting times or use async communication to reduce the burden on any single timezone.