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IST to PST Time Converter: How It Works

Updated · Standard formula, shown below

The calculator for this page is switched off while it is checked. The formula is below, and the worked example in the article shows how to use it by hand.

This tool converts a time from Indian Standard Time (IST, UTC+5:30) to Pacific Standard Time (PST, UTC−8) or Pacific Daylight Time (PDT, UTC−7), depending on the date. Enter a time in IST and you get the corresponding Pacific time, with the correct offset applied automatically for standard or daylight saving periods.

Formula

The conversion uses the fixed offset between IST and Pacific time. IST is always UTC+5:30. Pacific time is UTC−8 during standard time (PST) and UTC−7 during daylight saving time (PDT). The difference is therefore:

  • IST to PST: subtract 13 hours and 30 minutes (5:30 + 8:00).
  • IST to PDT: subtract 12 hours and 30 minutes (5:30 + 7:00).

In the calculator, the time is handled as minutes after midnight. The formula subtracts 450 minutes (7.5 hours) for PDT or 510 minutes (8.5 hours) for PST, depending on the month of the date you enter.

Worked Example

Take the default input: 12:00 IST on 2025-06-15. June is in the daylight saving period (the calculator uses a simple month-based rule: March through October). So the offset is 12.5 hours.

  1. 12:00 IST = 720 minutes after midnight.
  2. Subtract 450 minutes (PDT offset): 720 − 450 = 270.
  3. 270 minutes after midnight = 4:30 AM.

The result is 4:30 AM PDT on the same date. If the date were in January (standard time), the offset would be 510 minutes, giving 3:30 AM PST.

When to Use This Converter

Use this tool when you need to schedule a meeting, call, webinar, or any event across the IST–Pacific time zones. It is especially useful for remote teams, international business, travel planning, or watching live events broadcast from the other side of the globe. The converter handles the 12.5- or 13.5-hour difference automatically, so you don’t have to remember which offset applies on a given date.

How the Offset Changes with Daylight Saving

The Pacific time zone observes daylight saving time in most of its area (California, Washington, Oregon, Nevada, British Columbia). Clocks move forward one hour on the second Sunday in March and back on the first Sunday in November. IST does not observe daylight saving, so the offset changes only because the Pacific side changes.

  • From March to November: PDT (UTC−7) → IST is 12.5 hours ahead.
  • From November to March: PST (UTC−8) → IST is 13.5 hours ahead.

The calculator uses a simplified month rule (March–October) which is accurate for most dates, but for the exact transition days you should check the specific dates of the clocks changing.

Common Mistakes and How to Avoid Them

The most frequent error is forgetting the 30-minute offset. IST is not on the full hour; it is UTC+5:30, so the time difference is never a whole number of hours. Another mistake is assuming the same offset all year – the 13.5-hour difference only applies during Pacific standard time. Also, when you convert from IST to Pacific, the date can shift: if it is early morning in IST, the Pacific time will be the previous day. For example, 1:00 AM IST on June 15 is 12:30 PM PDT on June 14.

How to Read the Result

The output shows the Pacific time on the same date as your input, unless the subtraction crosses midnight, in which case the date rolls back one day. The result is displayed in 24-hour format (e.g., 16:30 for 4:30 PM). If you need the date, note that when the IST time is between 12:00 AM and 12:30 PM (during standard time) or 12:00 AM and 11:30 AM (during daylight time), the Pacific date is one day earlier.

Limitations and Notes

This calculator assumes the Pacific location observes daylight saving time as described. Some regions within the Pacific time zone (like Arizona, which is mostly Mountain time) do not follow this pattern, but for the core Pacific zone the rule holds. The month-based rule is accurate for most of the year, but on the exact transition dates (second Sunday in March, first Sunday in November) the offset changes at 2:00 AM local time, so the calculator may be off by an hour for those specific days. For precise scheduling on those dates, consult an official time zone database.

Frequently Asked Questions

What is the time difference between IST and PST?

IST is 13 hours and 30 minutes ahead of PST. So if it is 2:00 PM in India, it is 12:30 AM on the same day in Pacific Standard Time.

Is the difference the same all year?

No. During Pacific Daylight Time (mid-March to early November), the difference is 12 hours and 30 minutes. During Pacific Standard Time (early November to mid-March), it is 13 hours and 30 minutes.

Why is IST on a half-hour offset?

India chose UTC+5:30 in 1906, based on the longitude of 82.5°E, which passes through Mirzapur. The half-hour offset keeps sunrise and sunset times consistent across the country.

Does the date change when converting?

Yes, often. Because IST is far ahead, late evening in India corresponds to early morning the same day in Pacific time, but early morning in India corresponds to the previous afternoon in Pacific time. For example, 5:00 AM IST on June 15 is 4:30 PM PDT on June 14.

How do I convert IST to PST manually?

Take the IST time, subtract 13 hours and 30 minutes (for PST) or 12 hours and 30 minutes (for PDT). If the result is negative, add 24 hours and subtract one day from the date.

Related

Formula used
in t | Time in IST (HH:MM) | - | 12:00 | 0
in d | Date in IST | - | 2025-06-15 | 0
out pst | Pacific Time (PST/PDT) | - | t - (if(month(d)>=3 and month(d)

Each line is one input (in, sel, list) or one result (out: label, unit, formula, decimals). How the calculators work

Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.