{"id":1737,"date":"2026-10-12T18:28:25","date_gmt":"2026-10-12T18:28:25","guid":{"rendered":"https:\/\/www.tiwaripedia.com\/index.php\/2026\/10\/12\/india-one-time-zone-ist\/"},"modified":"2026-10-12T18:28:25","modified_gmt":"2026-10-12T18:28:25","slug":"india-one-time-zone-ist","status":"publish","type":"post","link":"https:\/\/www.tiwaripedia.com\/index.php\/2026\/10\/12\/india-one-time-zone-ist\/","title":{"rendered":"Why Does India Have Only One Time Zone? Understanding IST"},"content":{"rendered":"
\"Infographic:<\/figure>\n

When it is 6:00 am in Delhi, it is also 6:00 am in Kohima and in Bhuj, even though the Sun rises much earlier in the Northeast. That is because India uses a single time zone: Indian Standard Time (IST)<\/strong>.<\/p>\n

How do time zones work?<\/h2>

Earth rotates 360 degrees in 24 hours, so it turns 15 degrees every hour<\/strong>. The world is therefore divided into time zones roughly 15 degrees of longitude wide, measured from the Prime Meridian (0\u00b0) at Greenwich as Coordinated Universal Time (UTC)<\/strong>.<\/p>\n

How IST is calculated<\/h2>

IST is based on the 82.5\u00b0E<\/strong> longitude, which passes near Mirzapur in Uttar Pradesh. Since 82.5 \u00f7 15 = 5.5, IST is UTC + 5 hours 30 minutes<\/strong>.<\/p>\n

India is wide<\/h2>

India stretches about 30 degrees of longitude from Gujarat to Arunachal Pradesh, about two hours of difference in solar time. In the Northeast, the Sun can rise around 4:30\u20135:00 am in summer, while in western Gujarat it rises much later.<\/p>\n

The case for two time zones<\/h2>
  • People in the Northeast lose daylight hours when offices open by IST.<\/li>
  • An earlier time zone could save electricity and improve productivity there.<\/li>
  • Tea gardens in Assam have long followed an informal “chai bagan time”, about an hour ahead of IST.<\/li><\/ul>\n

    The case for one time zone<\/h2>
    • Simplicity for railways, flights, banking and broadcasting.<\/li>
    • Avoids confusion from switching clocks across state borders.<\/li>
    • Supports a sense of national unity.<\/li><\/ul>\n

      Other countries<\/h2>
      • China<\/strong> is even wider but also uses one time zone.<\/li>
      • The USA<\/strong> and Russia<\/strong> use several time zones.<\/li>
      • Nepal uses UTC+5:45, one of the few zones offset by 45 minutes.<\/li><\/ul>\n

        IST is maintained by the CSIR\u2013National Physical Laboratory in New Delhi using atomic clocks.<\/p>","protected":false},"excerpt":{"rendered":"

        India stretches nearly 3,000 km from east to west but uses a single time zone, IST (UTC+5:30). Learn how time zones work, why IST is set at 82.5\u00b0E, and the debate over two time zones.<\/p>\n","protected":false},"author":1,"featured_media":1736,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[336],"tags":[],"_links":{"self":[{"href":"https:\/\/www.tiwaripedia.com\/index.php\/wp-json\/wp\/v2\/posts\/1737"}],"collection":[{"href":"https:\/\/www.tiwaripedia.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.tiwaripedia.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.tiwaripedia.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.tiwaripedia.com\/index.php\/wp-json\/wp\/v2\/comments?post=1737"}],"version-history":[{"count":0,"href":"https:\/\/www.tiwaripedia.com\/index.php\/wp-json\/wp\/v2\/posts\/1737\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.tiwaripedia.com\/index.php\/wp-json\/wp\/v2\/media\/1736"}],"wp:attachment":[{"href":"https:\/\/www.tiwaripedia.com\/index.php\/wp-json\/wp\/v2\/media?parent=1737"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.tiwaripedia.com\/index.php\/wp-json\/wp\/v2\/categories?post=1737"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.tiwaripedia.com\/index.php\/wp-json\/wp\/v2\/tags?post=1737"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}