"One ad every 5 seconds": a Vietnamese ad agency built a quiet lunar calendar app that got 24k installs in three months

Vietnamese people check the lunar calendar and auspicious hours every day, yet the veteran lunar calendar app with tens of millions of installs is getting criticized for "screens full of ads". A Vietnamese app-advertising agency seized the moment and built a "quiet version" called Clarity, which got 24k installs in three months. The pain point is real, but it hasn't yet proven that "quiet" translates into growth. Below: what it is, where the volume comes from, its weak spots, and whether the idea is worth taking to other countries.

A one-star review with 21 likes

Oct 2026, 8, a user in Vietnam gave the long-running Lịch Vạn Niên 10.9 (Zegome) a one-star review, with 2026M installs: "đang xem ngày mà cứ 5 giây quảng cáo lần, xóa bỏ cho đỡ tức" — they were looking up the date when an ad popped up every 5 seconds, so they uninstalled to stop getting angry. That review got 21 "helpful" votes. Same month, another person wrote, "Opening the calendar is just ads, you can't even close them, everyone please don't download," and a review on another app, VMB, said, "Ads cover the whole screen, how would old people know how to close them" (Google Play reviews, 9–October).

Going through the recent 1–2 star reviews for these two apps: 42 of Zegome's 52 reviews complain about ads, and 60 of VMB's 83 reviews do. "Too many ads" is the most common complaint in the Vietnamese lunar calendar category.

Clarity is aimed squarely at this. Its Vietnamese Google Play page says: "Khác với các app lịch âm truyền thống nhiều quảng cáo……" (Unlike traditional lunar calendar apps with lots of ads…), and it promises something "minimal, accurate, calm."

What it is

A Vietnamese lunar calendar app, titled "Lịch Âm Dương 2026 - Clarity" in the Vietnam store and "Clarity: Lunar Calendar" in the US store. Launched in Aug 3 2026, categorized under Lifestyle.

The features are standard for the category: Yin-Yang date conversion, Heavenly Stems and Earthly Branches, zodiac animals, auspicious and inauspicious hours, lucky and unlucky days, holidays, lunar-solar conversion, and birthday and anniversary reminders. Two things stand out:

• The interface looks like a paper calendar: beige paper texture, plenty of white space, clear type.
• "Tinh Hoa Ngày" (Daily Essence): based on the five elements and the stems and branches, combined with your birthday, it gives a short daily guidance line. The page explicitly says "not superstition, not fortune-telling." This is both the reason to open it every day and the main selling point of the paid version.

How it makes money: the free version has ads (the store listing says "contains ads", and the description says "free users see unobtrusive ads"). Premium removes ads, unlocks personalized daily essence, unlimited notes, and themes, with in-app purchases of $1.99–$19.99 (Google Play Vietnam page, 11-06). So it isn't "ad-free"; it's "fewer ads, plus paid ad removal."

How big is it, and where does the traffic come from

Start with the numbers (cumulative installs estimated by AppstoreSpy plus Google Play, as of 11-06):

Normally 150–400 installs a day, with a spike of 1,000–2,000 a day every few weeks (10-03 +1,284,10-07 about +1,949,10-31 +1,004,11-02 +1,129). Over the last 7 days: +3,200. The Vietnam page has a 4.4 rating from 29 reviews and shows "10k+" downloads. It only appears on the Vietnam storefront's Lifestyle free chart, ranking 31–41.

The bar here is low: Zegome, #2 on the same chart, gained 44k a week, 14× what Clarity got.

Behind it is an ad agency. The developer is listed as "B - Studio", and the bio ends with "Developed by TMR Team". TMR stands for The Masters Reach, a Vietnamese App growth agency doing UA, ASO, cost-per-install ad buying, and AdMob monetization. Their homepage line reads: "What TMR does for you, TMR has already done on its own products." Three in-house apps hang off it: a diary app, this lunar calendar, and a match-3 game. The App Growth page cites "Lịch Âm Dương Clarity 10k+ downloads, 4.4 rating" as a case study (themastersreach.com, 11-06).

The traffic is most likely bought (inference). Its YouTube channel "TMR Team" has only 746 subscribers but 6.33M total views. From August 17–29 it posted 5 Clarity videos with 104k, 97k, 57k, 26k and 3k views. The promo video embedded on the store page (posted 08-17) has 56,663 views, 0 likes and 0 comments (YouTube, 11-06). Tens of thousands of views with almost no likes strongly suggests the views came from Google video ads or app promotion. The timing fits too: late August is when installs started. The install pulses every few weeks since then look like budget released in batches.

Store search is confirmed. The Vietnamese store title uses the search term people actually type, "Lịch Âm Dương 2026". The short description reads "Personalized lunar calendar, Can Chi, auspicious hours, daily highlights", and the description is stuffed with Can Chi, Giờ Hoàng Đạo, Ngày tốt xấu and 12 Con Giáp. The English brand name appears only in the US store. This is standard ASO.

Not found: no TikTok, X or press coverage turns up. The iOS version went live in Aug 12, English only, with 0 ratings, and has not been promoted yet.

What users say

There are few reviews, and they are specific (Google Play Vietnam page, 11-06):

• 10-28, Sang Pham: "sai tot ok khog quang cao" (no tone marks; roughly: works well, no ads).
• 10-17, Phước Mạc: "It doesn't update on its own, and the date is wrong unless you open the app." They mean the home screen widget.
• 10-28, Thuý Thanh: her mom wanted to see the month calendar as soon as she opened it, but it opened to the day view every time. "So annoying I wanted to delete the app."

The developer replied to each one in Nov 2: the widget date bug is fixed, and the look was changed to a "vintage beige paper" texture; pinning the month view is coming in the next version.

These reviews show two things. First, people do care that it has no ads. Second, for a calendar you glance at every day, whether the widget is accurate and what you see on open matter far more than how it looks. Many of its users are older, and older users want to open the app and see this month.

Who it's competing with

This is a decade-old category, and the leaders have been on the store for 2013–2017 years (Google Play, 11-06):

There are two more free rivals. One is the phone's built-in calendar: iPhone and Samsung can both show the lunar calendar, and a TikTok tutorial on "how to set up the lunar calendar on iPhone" has 1.06M views. The other is the web: VnExpress, VietnamNet and xemlicham.com all have free almanac pages, taking the search traffic directly.

Nhất Nam's title keywords are almost identical to Clarity's, and it is 180× bigger. Search "Lịch Âm Dương" in the store and newcomers are competing with these apps for the same term.

Is "quiet" the reason it's gaining traction?

Not so far. Its volume is flat, a few hundred installs a day, propped up by occasional promotion. 29 ratings at 4.4 stars suggest users find it acceptable, but there is no sign anyone recommends it specifically for having no ads. TMR built this app first as a case study to show agency clients, so how much the app itself earns is secondary (inference).

The pain point is real and the approach fits it, but nothing yet shows it turns into growth. From the outside there is no way to tell whether Vietnamese users would pay a few dollars a year for a calendar.

If it were you

C. Worth studying, not worth copying. Old almanacs are ad-heavy, so the pain point is real. But this category has tens of millions of long-time users, the system calendar and web pages are free, Vietnamese users have low willingness to pay, and Clarity has not yet shown that a "quiet version" can grow.

Who it suits: a small team that already runs Google app promotion and does ASO, has a working lunar and Can Chi algorithm, and wants a utility app that steadily picks up search volume and slowly pays back through ads plus an ad-free in-app purchase. Or a team like TMR that wants an in-house case study to win agency clients.

Who it doesn't suit: anyone counting on good design to bring in users organically; anyone who can't run paid acquisition and is relying on word of mouth; anyone aiming at the Chinese-language almanac market (it's more crowded, with big-company calendar and weather apps that already include the traditional almanac).

How to do it: don't go to Vietnam, which already has five or six apps at the ten-million level plus a quiet version. Pick a market where people also check the lunar calendar daily, where old apps are heavy on ads, and where no quiet version exists yet: Cambodia (Khmer Lunar Calendar has 11.7M installs), Korean lunar calendar, Indian Panchang, Thailand. Follow Clarity's playbook: an accurate calendar, a personalized daily guidance line, free with fewer ads and an ad-free paid upgrade. Get the home screen widget accurate first, and have the app open to the month view by default. These two things are what older users actually use every day.

How to acquire users: put the term locals search for plus the year in the title (in Vietnam, "Lịch Âm Dương 2026"), spend a small budget on Google app promotion, and answer negative reviews one by one.

Deadline: launch before the biggest traditional holiday in your target market. For Korea, that's Seollal in early February 2027; for Cambodia, before Khmer New Year in mid-April. People check the lunar calendar more before holidays, and if you miss the window you wait another year.

What would prove the call wrong: ① Clarity survives 2027 Lunar New Year, daily installs rise from hundreds to thousands, and the rating count passes a thousand. That would show a "quiet version" can actually pull users from the old apps, and then expanding to other markets is worth serious effort. ② The reverse: if daily installs don't clearly rise during the holiday peak, or drop to a few dozen a day after TMR stops buying ads, the angle isn't producing growth. ③ Zegome or VMB launch a "paid ad-free" tier or cut their ads. Once the pain point is covered for the old players, newcomers have no reason left.