A birth time calculator built by an Istanbul data engineer: #9 on Turkey's iOS overall free chart, with almost no competitors in the store

Turks love talking about rising signs, but knowing your rising sign requires knowing the exact minute you were born, and many people only know it was "roughly in the morning." Ömer Faruk Ballı, a data engineer in Istanbul, built a phone app for exactly that: Retrace: Birth Time Explorer. You enter a time window and log a few major life events, and it figures out which minutes in the window fit best. It launched on iOS in Oct 10, reached #26 on Turkey's iOS overall free chart by Oct 9, and launched on Android in Oct 23, reaching 4 installs by Nov 2,217. It's small and Turkey-only, and few people know about it. Below: what it is, where the traffic came from, where the money comes from, who the competition is, and whether you can follow it.

"I had it corrected by an astrologer and it's only off by 5 minutes"

On Oct 26, a Turkish user left a five-star App Store review with specifics: "I used to pay an astrologer to do rektifikasyon (birth time correction). To test this app, I pretended I had no idea of my birth time and only gave it a range to search. The result was only 5 minutes off from what my astrologer said, and I think that's pretty OK. If you could add a few more events, like the date I started university or my siblings' birthdays, I think those 5 minutes could be closed."

The next day, another review: "I only know my birth time because I had it corrected, and here it's only 2–3 minutes off, really impressive 🧿." Another: "I gave it a 1-hour window and it still gave me an accurate minute."

On the evening of Oct 28, the Turkish astrology account @kayratarot reposted one of the developer's replies on X with the comment: "For people who don't know their birth time, this is a very successful app. At least it finds a close time. It makes you proud that someone is building things like this in this field." (X, 10-28)

Interestingly, the developer's own store page and personal website say something different: he tested it on 110 cases with known birth records and found "the peak isn't any more likely to point to the true birth time than a random time." That line has stayed on the app's results page. Almost no users mention it. They want a tool that "calculates my birth time," and once they get one, they go to the comments and say it's accurate.

What it is

A birth time correction calculator on your phone, using Western astrology algorithms:

• Enter your birthday and birthplace, then pick a time window (morning, noon, afternoon, night, or a custom range);
• Answer questions about your life one by one: marriage, moves, having kids, job changes… fill in as many dates as you remember, or just the month, season, year, or even "how old I was then";
• The results page shows which minutes in the window have the most astrological "contacts" with those events, explains why each event was included, and displays the chart, letting you see how the rising sign changes across the window. House systems include Whole Sign and Placidus;
• Everything is calculated on your phone, with no sign-up and no data uploaded. Under the hood is a C++ core, with a separate native interface written for iOS and Android (developer's personal site).

The store page says it supports 50 languages, but Turkish is the only market with visible traction.

Why it took off in Turkey

Dense demand. Turkey has a large astrology community, and rising signs depend on birth time. Many people only have a rough birth time, or the records in the government system e-Devlet are unreliable. TikTok videos teaching people "how to recover your birth time" get hundreds of thousands to millions of views (one by @tuanayucel reached about 1.5M, one by @ozancankubilay about 400k), and one is titled outright "The birth times you get from e-Devlet are mostly wrong."

The old options were expensive or hard. Astrologers offer birth time correction, and platforms like armut.com have more than forty consultants taking bookings. You have to schedule a time and pay hundreds to thousands of lira. Web tools like Astro-Seek are free, but their interface is built for people who already understand primary directions. Retrace turns it into a question-and-answer flow, lets you enter vague dates, and gives results on the spot.

The developer is part of this circle. On X he goes by @omerryjane, he already hung out in Turkish astrology Twitter, and he also built a free web astrology site, kozmikatlas.com. The promotion was simple: reply under astrology accounts' posts with "I built a rektifikasyon app that calculates birth time to the minute, available on Google Play and iPhone," plus a link. The same day, he also replied under someone else's post saying "the new calculation engine has 59 detailed event types."

A timing point to be clear about: iOS hit the overall chart at #9 on Oct 26, the reviews clustered on Oct 25–27, and the @kayratarot endorsement came out on Oct 28. So it wasn't that post that pushed it onto the chart. More likely he had already posted a thread earlier, and a few astrology accounts picked it up one after another (inference). One 1-star review (10-26) also says, "you already run ads on X and other platforms," and it's unclear whether that's paid ads or his own promo posts.

Scale

(Android figures are the install counts shown on Google Play)

The Android "+1,418 in a single day" is most likely not all from one day: Play's install counter lags, and the app had already reached the top-grossing chart in the days when the count still read 17. That shows people were installing and paying earlier, and the count was caught up in one jump on Nov 1 (inference).

Overall, it was a small burst: the best iOS Turkey utilities top-grossing rank was #70 (11-01), then it fell to 135 and 196. Android has barely grown since Nov 3.

Where the money comes from

One-time purchase, no subscription. The free version allows 1 cases and 4 events in total. The Premium one-time purchase allows 3 cases with unlimited events, plus a PDF report. Pro costs more, with unlimited cases and adjustable weights and tolerance. The Google Play in-app prices run $2.99–$9.99, and Turkish reviewers mention "249 lira."

The free tier is very tight: 4 events is just enough to see one result, not enough to verify it. Negative reviews mostly complain about this: "You only let me add 4 things," "Everything costs money, give a trial period first," "One wrong entry uses up your quota and it immediately pushes Pro." But that same wall is what got it onto Turkey's top-grossing charts.

Revenue hasn't been disclosed. Turkey's utilities top-grossing chart ranks a hundred or two hundred apps, and its iOS category top-grossing best was #70. Both bars are low, so my estimate is a few to a few dozen sales a day, in the low thousands of dollars cumulatively.

Who it's competing with

Searching "birth time" and "rectification" on Google Play turns up one native app built specifically for rectification for ordinary people (Google Play, 11-06). I also don't see anyone copying it; the only other thing is a "birth time rectification API" (astrology-api.io), which suggests people want this feature inside other astrology apps.

If it were you

B: The gap is real and not hard to build, but the market is small, this wave is already fading, and someone in the local astrology scene has to vouch for you.

Who it's for: Indie devs who know some astrology (or are willing to seriously learn one system) and can write a phone app. Ideally you're in a country with a heavy astrology scene, or you can work with a local astrology blogger.

Who it's not for: Anyone looking for a big business. This is a narrow tool sold as a one-time purchase, used once, with little repeat buying. Also skip it if you find astrology itself off-putting or don't want to face the "does this actually work" question.

How to build it: Use its recipe, but change the country and the system. There are several markets with heavy astrology demand and people who can't remember their birth time: Brazil, Mexico (Spanish / Portuguese), India (you'd need Vedic or KP, which locals trust), and English-speaking markets, where Co-Star's users also get stuck on "I don't know my birth time." For the product, focus on three things: guided Q&A, fuzzy dates allowed, and an on-the-spot "most likely minute." The gaps in the original are your opening: the free tier is stingy, wrong entries can't be edited, there are few event types (users ask for things like "started university" or "sibling born"), and there's no trial period. You could go one step further: after calculating the time, add a rising sign reading, or sell it as a feature to other astrology apps.

How to get users: You can start without paid acquisition. Reply to local astrology bloggers' posts and message them to try it, demoing with their own birth times. Astrology bloggers get asked "what if I don't know my birth time?" all the time, so you're helping them answer their audience. Comment sections on TikTok videos about "how to find your birth time" are ready-made audiences. Entry bars are low in small countries, so one wave of endorsements can push you into the top of the free overall chart, and then rankings and search can carry it.

When's the window closing?: There's no hard deadline, but you want to move before it fully rolls out to 50 languages. The developer ships fast (1.1.1 updates a month), and once they find their next astrology hit in Brazil or the English markets, those gaps are gone.

What would mean you read it wrong: If its Turkish top-grossing rank keeps sliding past #200 and ratings stay stuck in the forties, it's a one-time curiosity in one circle, used and dropped, and the same would happen in any other country; if a few months from now it charts in other countries, the demand is broad, and entering then is too late, so you'd need to target the system it doesn't cover (Vedic) or a different audience.