The clock on your phone knows Peninsular Malaysia skipped half an hour

On 31 December 1981, clocks in Peninsular Malaysia went from 11:30 pm straight to midnight. The new year began half an hour early. The peninsula moved from UTC+7:30 to UTC+8, which means from seven and a half to eight hours ahead of UTC, the world reference clock. The clock on your phone still knows it happened.

Why the peninsula moved

The National Archives of Singapore records that "the Malaysian Government announced in December 1981 that it would adjust Peninsular Malaysia's time by 30 minutes on 1 January 1982 in order to keep common time with East Malaysia." Sabah and Sarawak were already on UTC+8, half an hour ahead of the peninsula, and did not change.

Singapore followed at the same moment, the archive says, "to prevent confusion for travellers and businessmen".

The change was made into law as the Malaysian Standard Time Act 1981. We have not read the Act's text at source, so we do not quote it here.

Earlier changes on the peninsula

The time zone database records every change it has found for the peninsula. Kuala Lumpur kept its own local time, 6 hours 46 minutes and 46 seconds ahead of Greenwich, until 1901. Then came Singapore Mean Time, then UTC+7 from 1905, UTC+7:20 from 1933 and UTC+7:30 from September 1941.

From 16 February 1942 to 12 September 1945, the peninsula and Sabah and Sarawak were on UTC+9. The database does not label the period. The National Archives of Singapore does: "Time had to be adjusted again during the Japanese Occupation with the introduction of Tokyo time."

The database credits these Malaysian and Singapore entries to Mok Ly Yng, whose research it adopted in 2003.

How your phone gets the rules

The Time Zone Database, also called tz, is a free list of the clock history of places around the world. IANA publishes it. Volunteers maintain it, and its data is in the public domain.

1. A government changes its clocks.
2. Volunteers update the database. A new release typically comes out every few months.
3. Phone and computer makers copy the release into their software. The database's own list of users includes Android, iOS, macOS and the GNU C Library used in Linux. Windows is different: it keeps its main time zone data in its own Registry, and uses the database only for its newer app framework.
4. Your device downloads the update and uses it to turn world time into the time on your screen.

There is a delay at step 3. The database's documentation warns that "older devices may no longer be supported and thus may never be updated, which means they will continue to use out-of-date rules." It asks governments for at least a year's notice. They do not always give it.

In March 2023, Lebanon announced a delay to its summer time change days before it was due. The database's notes record that Google went with the announcement and Apple did not, and that Beirut airport listed two times for each departure. The government later backed down. This year, release 2026e came out on 29 September with a change for Manitoba, Canada, due on 31 October.

Who looks after it

Arthur David Olson started the database and was its first maintainer, at the US National Institutes of Health.

Today IANA names Paul Eggert and Tim Parenti as the coordinators. Eggert is a senior lecturer at UCLA. UCLA reported in 2022 that he does this work without pay. "It's just a hobby," he told them.

In September 2011, an astrology software company, Astrolabe, sued Olson and Eggert. It claimed copyright in an atlas the database partly relies on. The Electronic Frontier Foundation defended them. On 22 February 2012, Astrolabe withdrew its complaint, apologised and agreed not to sue again. There was no court ruling.

In October 2011, ICANN announced it would manage the database. RFC 6557, published in February 2012, set out the new arrangement. It says the database had been coordinated by "a single volunteer who is now planning to retire." It also says the data "is in the public domain" and that ICANN and the IETF Trust will make no ownership claims.

What happened to Kuala Lumpur

Kuala Lumpur's entry in the database is named Asia/Kuala_Lumpur. Since release 2022b in August 2022, it has not been its own entry in the database's main data. It is now a link to Asia/Singapore. The name still works on your devices, and the times since 1970 are the same. Kuala Lumpur's earlier history is kept in a separate file.

This follows a general rule the maintainers set out: "If all clocks in a region have agreed since 1970, give them just one name even if some of the clocks disagreed before 1970." When merging, they keep the entry for the most populous location. The policy was contested in 2021. LWN reported that the maintainer of Joda-Time, a widely used date library, "disagreed strongly" and asked for a revert; Eggert defended it. We found no source that discusses Kuala Lumpur in that dispute.

What this means for your business

LHDN's MyInvois FAQ lists an error, "Document issuance date and time is in the future", and gives the cause as a time that "does not comply with the required UTC standard". UTC is eight hours behind Malaysian time. The FAQ also says the issue time must be "within 72 hours before submission". A system set to the wrong time zone can trip those rules.

Ask whoever runs your invoicing which time zone it stamps your e-invoices with. Then check that the old PC or till that stamps your records still gets updates and shows the right time. This piece makes no legal claim; ask your adviser if that matters to you.