ASEAN Common Time is an idea proposed by the Association of Southeast Asian Nations to adopt a standard time of UTC+08:00 for all member countries. Some regional businesses have already begun adopting the phrase "ASEAN Common Time," and often use the abbreviation ACT in their press releases, communications, and legal documents.
But some commentators suggest using UTC+07:00 instead, as UTC+08:00 would create problems in the Kachin State of Myanmar during summer months, with a late sunrise taking place at 07:20 and a late sunset at 20:45. Other experts advocate calling UTC+08:00 ASEAN Central Time, putting Myanmar at UTC+07:00, and leaving less populous eastern Indonesia at UTC+09:00.
This would result in the vast majority of the region's people and territory lining up at UTC+08:00—in sync with China, Hong Kong, Macau, Taiwan, and Western Australia. The eastern islands of Indonesia would remain at UTC+09:00—in sync with South Korea, Japan, Palau, and East Timor.
The four different time zones currently used by ASEAN countries are UTC+06:30 (Myanmar); UTC+07:00 (Cambodia, Laos, Thailand, Vietnam, and western Indonesia); UTC+08:00 (Singapore, Malaysia, Brunei, Philippines, and central Indonesia); and UTC+09:00 (eastern Indonesia).
Citations
Abdullah Ahmad Badawi: "... in order to keep ASEAN with the people, ... some possibilities come to mind, such as an ASEAN common time zone...".
The Nation, December 1996: "...deferred a plan for the creation of a common Asean time zone ..."
"The idea has since been under discussion by ASEAN, with Singapore supporting it strongly."