Don't download a lunar calendar app for iPhone.

iOS 26 now includes a lunar calendar on the iPhone system.

During the Lunar New Year, Vietnamese people switch to using the lunar calendar to plan many events. However, most phones only support the Gregorian calendar. Previously, only Samsung phones came pre-installed with a Vietnamese lunar calendar version. With iPhones, users had to download additional apps to view it when needed. These apps frequently climb to high positions on the App Store rankings during the Lunar New Year season.

However, starting this year, Apple device users no longer need to use extra storage or watch ads to experience such services. Specifically, in iOS 26, Apple has a feature dedicated to Vietnamese users. The system calendar has been updated with a Lunar calendar version specifically for the domestic market.

To activate this feature, users go to Settings, open the Apps section, and select Calendar. Here, the alternative Calendar settings include the Vietnamese Lunar Calendar in the list. Once enabled, this option will display the Lunar Calendar on the lock screen or in the date viewing app, making organization simpler and more efficient.

For the 2024 Lunar New Year, several Facebook pages shared tips on using an add-on feature in the default iPhone app to view the lunar calendar directly on the phone, without needing to open a website or download a third-party app. Many users followed these tips because they noticed the similarity. However, this method does not provide accurate lunar calendar information.

Specifically, many accounts advise users to enable the Jewish calendar feature in iOS settings to view the lunar calendar. When activated, in addition to the Gregorian dates, the device also displays the dates according to the Jewish calendar. In this month, the dates in the aforementioned calculation method and the lunar calendar coincide. Therefore, many people believe and follow this advice.

However, the Jewish calendar and the lunar calendar used in Vietnam are not exactly the same. For example, the 1st day of the 2nd lunar month of the Year of the Dragon (Giáp Thìn) falls on March 10th (Gregorian calendar). Meanwhile, the first day of the 2nd month of the year in the Jewish calendar is March 11th (Gregorian calendar). Thus, the two methods of calculation differ by one day.

Furthermore, the Jewish calendar has a different way of naming months compared to the Gregorian and Lunar calendars. Therefore, it can be difficult for users to follow when additional settings are enabled on their iPhone.

In fact, the Jewish calendar and the lunar calendar used in countries like Vietnam, China, and Singapore have similarities. They both use a calculation method that combines the rotations of the Moon and the Sun. Each month has 29 1/2 days, corresponding to the lunar cycle. Furthermore, in these calendars, every 19 years there are 7 leap years, each with 13 months. This is to ensure the Earth completes a full orbit around the sun within a calendar year.

However, the arrangement of months with 29 or 30 days and leap months in the Jewish and Lunar calendars is not the same. Even among countries that share the same lunar calendar, such as Vietnam, China, South Korea, and Singapore, there are years with discrepancies in dates due to different calculation methods.