{
  "id": "india-time-zones",
  "version": "745ccfd950b0",
  "status": "published",
  "name": "India Time Zones",
  "question": "How many India time zones?",
  "summary": "Lists the time zones of India with the local time, abbreviation, UTC offset, and daylight saving in each, for any time and date.",
  "category": "days",
  "subcategory": "time-and-hours",
  "url": "https://www.acalculator.org/days/india-time-zones",
  "markdown": "https://www.acalculator.org/days/india-time-zones.md",
  "kind": "function",
  "method": "For the typed time in the chosen zone, find the instant (UTC) it names, then show each listed zone’s clock at that instant with its UTC offset, from the browser’s IANA time zone data.",
  "assumptions": [
    "The zones are IANA tzdata names from zone1970.tab (tzdata 2026a): Asia/Kolkata. The browser supplies each zone's offsets and daylight saving rules, so a rule change arrives with a browser update.",
    "“Time zones” counts the different standard offsets among the listed zones. A zone’s standard offset in a year is the lower of its offsets at 00:00 UTC on January 1 and July 1 of that UTC year.",
    "“UTC offsets in use” counts the different offsets the listed zones show at that moment.",
    "Each zone shows its local time, the abbreviation from the browser’s Unicode CLDR English names (left out when CLDR has none), the date as “Tue, Sep 29”, the offset as UTC+hh:mm or UTC−hh:mm, and “daylight saving” when the offset is ahead of the standard offset, “standard time” when the zone’s January 1 and July 1 offsets differ but it is on the standard offset, or “no daylight saving” when they are the same. Because the rule compares January 1 and July 1, a zone that moves its offset for good during a year (Cancún in 2015, Novosibirsk in 2016), or whose January 1 falls in Morocco’s Ramadan change (Casablanca in 2030 to 2033), shows the later offset as “daylight saving” for that year.",
    "A time that does not exist in the chosen zone (skipped when clocks spring forward) has no answer. A time that occurs twice (when clocks fall back) shows both moments, earlier first, where they differ.",
    "Dates from 2000 to 2040 work."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "at": {
        "title": "Time",
        "description": "A clock time in the zone chosen below; the table shows that moment in every zone.",
        "type": "string",
        "pattern": "^\\d{2}:\\d{2}(:\\d{2})?$"
      },
      "zone": {
        "title": "In",
        "description": "The time zone of the time above (IANA name).",
        "type": "string",
        "enum": [
          "Asia/Kolkata",
          "UTC"
        ]
      },
      "on": {
        "title": "Date",
        "description": "The date of that time in that zone. Today, unless you change it.",
        "type": "string",
        "format": "date"
      }
    }
  },
  "outputs": {
    "zones": {
      "label": "Time zones",
      "description": "The number of different standard UTC offsets among the zones listed for India.",
      "format": "integer"
    },
    "inUse": {
      "label": "UTC offsets in use at that moment",
      "description": "The number of different UTC offsets the listed zones show at that moment, daylight saving included.",
      "format": "integer"
    },
    "kolkata": {
      "label": "India Standard Time: all of India",
      "description": "Local time, abbreviation, UTC offset, and daylight saving in Asia/Kolkata at that moment.",
      "format": "text"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "at": "12:00",
      "zone": "Asia/Kolkata",
      "on": "2026-09-30"
    },
    "outputs": {
      "zones": 1,
      "inUse": 1,
      "kolkata": "12:00 PM IST · Wed, Sep 30 · UTC+05:30 · no daylight saving"
    },
    "text": "At 12:00 PM on September 30, 2026 in India Standard Time: all of India, India has 1 time zone and 1 UTC offset in use."
  },
  "examples": [
    {
      "given": {
        "at": "12:00",
        "zone": "Asia/Kolkata",
        "on": "2026-01-15"
      },
      "expect": {
        "zones": 1,
        "inUse": 1,
        "kolkata": "12:00 PM IST · Thu, Jan 15 · UTC+05:30 · no daylight saving"
      },
      "source": "IANA Time Zone Database, tzdata 2026a (https://www.iana.org/time-zones); Python 3 zoneinfo with tzdata 2026a (2026-01-15T06:30Z); abbreviations from Unicode CLDR English names (docs/progress/WP-46/truth.py)"
    },
    {
      "given": {
        "at": "12:00",
        "zone": "Asia/Kolkata",
        "on": "2026-07-15"
      },
      "expect": {
        "zones": 1,
        "inUse": 1,
        "kolkata": "12:00 PM IST · Wed, Jul 15 · UTC+05:30 · no daylight saving"
      },
      "source": "IANA Time Zone Database, tzdata 2026a (https://www.iana.org/time-zones); Python 3 zoneinfo with tzdata 2026a (2026-07-15T06:30Z); abbreviations from Unicode CLDR English names (docs/progress/WP-46/truth.py)"
    }
  ],
  "sources": [
    "CSIR-National Physical Laboratory, New Delhi: Indian Standard Time",
    "IANA Time Zone Database, tzdata 2026a (https://www.iana.org/time-zones)"
  ],
  "related": [
    "time-zone-converter",
    "time-zones",
    "us-time-zones",
    "pdt-to-est",
    "europe-time-zones",
    "australia-time-zones"
  ],
  "changelog": []
}