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The Time Zone Converter calculates what time it is in a target location when you know the local time and both locations' UTC (Coordinated Universal Time) offsets. It handles wraparound across midnight and supports half-hour offsets used by time zones like India (UTC+5:30) and Iran (UTC+3:30).
Time zone conversions are a daily necessity in our globalized world. Remote work teams spanning New York (UTC−5), London (UTC+0), and Singapore (UTC+8) must constantly synchronize meetings across a 13-hour span. International travelers need to know arrival local time from departure time. Financial traders track market opening times in New York, London, and Tokyo simultaneously. Software developers schedule deployments during off-peak hours for users in multiple regions.
The converter works with UTC offsets — numerical hour values added to or subtracted from UTC to get local time. UTC−5 is 5 hours behind UTC (Eastern Standard Time), UTC+5:30 is 5.5 hours ahead (India Standard Time). By converting both source and target times through UTC as an intermediary, any pair of time zones can be compared without a lookup table.
Note: this calculator uses fixed UTC offsets and does not automatically apply Daylight Saving Time (DST) adjustments. During DST, many zones shift by +1 hour. Always verify DST status for your specific date.
The algorithm converts the source time to UTC, then from UTC to the target time zone:
$$T_{UTC} = T_{source} - \text{offset}_{from}$$
$$T_{target} = T_{UTC} + \text{offset}_{to} = T_{source} + (\text{offset}_{to} - \text{offset}_{from})$$
Expressed in total minutes from midnight:
$$M_{source} = H_{source} \times 60 + m_{source}$$
$$M_{target} = M_{source} + (\text{offset}_{to} - \text{offset}_{from}) \times 60$$
To handle day wraparound (results outside 0–1439 minutes):
$$M_{target,wrapped} = ((M_{target} \mod 1440) + 1440) \mod 1440$$
The double-modulo pattern ensures negative values (crossing midnight backward) also wrap correctly. The final target hour and minute are extracted as:
$$H_{target} = \lfloor M_{target,wrapped} / 60 \rfloor$$
$$m_{target} = M_{target,wrapped} \mod 60$$
The target hour and target minute give the local time at the destination. The time difference (positive = target is ahead, negative = target is behind) helps you remember which direction to adjust. If the result crosses midnight, the day also changes — this calculator does not show the day change, only the time. For international meetings, also consider whether the date is different: a +13 hour difference means it is literally the next calendar day at the destination.
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9:00 AM EST = 2:00 PM GMT. London is 5 hours ahead of New York (standard time, no DST).
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10:00 GMT = 15:30 IST. India's UTC+5:30 offset includes a half-hour, entered as 5.5.
A UTC offset is the number of hours (and sometimes half-hours) that a time zone differs from Coordinated Universal Time (UTC). UTC−5 means 5 hours behind UTC; UTC+5:30 means 5.5 hours ahead (enter as 5.5).
This calculator uses fixed offsets. When DST is active, adjust the offset by +1. For example, US Eastern Time is UTC−5 in winter (EST) and UTC−4 in summer (EDT). Always check whether DST is currently active for your region.
India (UTC+5:30), Sri Lanka (UTC+5:30), Iran (UTC+3:30), Afghanistan (UTC+4:30), Myanmar (UTC+6:30), and Australia's Northern Territory (UTC+9:30) use half-hour offsets. Enter these as decimal values (e.g., 5.5 for UTC+5:30).
The calculator wraps the time to the correct 0–23 hour range. For example, 10 PM + 5 hours = 3 AM (next day). The calculator shows 3:00 as the target hour. Note that the date is not shown — it is the next calendar day.
UTC (Coordinated Universal Time) is the primary time standard by which the world regulates clocks. It does not observe DST. All time zones are defined as UTC offsets. UTC replaced GMT (Greenwich Mean Time) for technical purposes, though they differ by less than 1 second.
The theoretical maximum is 26 hours (UTC−12 to UTC+14). In practice, the most extreme regularly inhabited zone difference is between Baker Island (UTC−12) and Kiribati's Line Islands (UTC+14).
Roboculator Team
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