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How to Choose a Saju App for Date Selection
— 5 Things to Check
Most Saju apps only go as far as a Son-eomneun-nal calendar. That's a date lookup, not taegil (date selection). There are five things to check — Does it take your Saju? · Can you choose a purpose? · Does it pick candidates within a date range? · Does it show its reasoning? · Does the chosen day carry over into your events?
In this article 9 topics
- What sets a Saju app with real date selection apart?
- Does an app with only a Son-eomneun-nal calendar count as date selection?
- What are the five things to check in a date-selection app?
- What should an app do for each purpose?
- Why do different apps give different "good day" results?
- How does Mutal Unnie's "Find a good day" work?
- Can't I just leave the chosen day as it is?
- What Mutal Unnie can't do
- FAQ
What sets a Saju app with real date selection apart?
Date selection isn't about pinpointing a date for you; it's about narrowing down candidates. So for an app to say it does date selection, it needs at least two inputs: your Saju and what you're planning to do.
| Category | Son-eomneun-nal calendar type | Date-selection type |
|---|---|---|
| What it asks for | Nothing (calendar only) | Date of birth + purpose + date range |
| Result | Same dates for everyone | Different candidates for each person |
| Criteria | Lunar date ending | Lunar calendar + zodiac clashes + the day's iljin tone + purpose |
| Shows reasoning | Usually not | The day's stem-branch pair and reasons for exclusion |
| Next step | Ends on the screen | Carries over into your events |
You need both. But it's common for an app you downloaded after searching "date selection app" to actually be the calendar type. You can tell within 5 minutes of installing — if it doesn't ask for your date of birth, it's the calendar type.
Does an app with only a Son-eomneun-nal calendar count as date selection?
It's a date lookup, not date selection. Son-eomneun-nal are days whose lunar date ends in 9 or 0, so they're the same for everyone, coming around 5 times in a short lunar month and 6 times in a long one. How many fall in a Gregorian month depends on how the two calendars overlap.
So a Son-eomneun-nal calendar is the starting point for date selection, not the conclusion. That calendar alone won't filter out days that clash with your zodiac animal. For example, for someone born in a Year of the Horse, a Ja (子) day is a direct clash — and that day could also be a Son-eomneun-nal.
I've written about the difference between date selection and Son-eomneun-nal in detail in What is taegil (date selection)? — what it means to choose a good day. You can see all the clashing pairs on one page in the zodiac compatibility table.
What are the five things to check in a date-selection app?
Once it's installed, just tap through them in order. If three or more of the five don't work, it's safe to call it a calendar-type app.
- Does it ask for your Saju?A "good day" given without your date of birth isn't a day chosen for you.
- Can you choose a purpose?Moving, weddings, openings and contracts each favor a different tone. If the app doesn't ask your purpose, it isn't making purpose-specific judgments.
- Does it pick candidates within a date range?Real life looks like "moving sometime in October," not "October 12." You need to be able to enter a start and end date for it to be useful.
- Does it show why that day?It should show the day's stem-branch pair, whether there's a clash and why days were excluded, so you can judge when it disagrees with another app.
- Does the chosen day carry over into your events?This is where most apps drop off. Close the screen and the date is gone.
What should an app do for each purpose?
Even on the same day, a good day for moving and a good day for a contract are different. If an app lets you choose a purpose, it should at least distinguish the following.
| Purpose | Fixed first | What the app should do |
|---|---|---|
| Moving | Final-payment day / lease end date | Rank candidates within the possible 2–4 weeks, mark weekends |
| Wedding | Venue availability | Look at both people's charts together (wedding date selection) |
| Business opening | Interior work completion date | Prioritize days with an expansive tone, consider the weekday |
| Contract | The other party's schedule | A tone that favors attention to detail, avoid clashes |
| Confession / blind date | The other person's schedule | Guidance on time of day is more useful than the date |
Reverse the order and it fails. If you pick the date first and try to fit everything else around it, you usually can't stick to it. The right order is to lock in the conditions you can't change, then choose within what's left. The full sequence is in How to choose a good day — complete guide.
Why do different apps give different "good day" results?
Because they look at different criteria to begin with. An app that looks only at Son-eomneun-nal, one that looks only at zodiac clashes, and one that also considers your personal chart and purpose are calculating different things entirely.
There's one more factor — which country's basis the lunar calendar is calculated on. Between a lunar calendar calculated in Korea Standard Time and one that simply copies the Chinese nongli calendar, there are 427 days between 1900 and 2050 where the Son-eomneun-nal verdict differs. Take Seollal 2027: it's February 7 by the Korean lunar calendar and February 6 by the Chinese nongli calendar.
So when results differ, it's better to go by the app that shows its reasoning. I've explained why they differ in Why manseryeok apps give different results.
How does Mutal Unnie's "Find a good day" work?
Enter a purpose and a date range, and it returns candidate dates based on your Saju. It's a feature built to follow the five checks above.
The third is where it parts ways with other apps. Most date-selection features end at the results screen. But the moment you actually need help isn't when you're choosing the date — it's when the day is approaching. In Mutal Unnie, adding events is free, with no limit on how many.
A note on the calculations, too. The lunar calendar is calculated in-house based on Korea Standard Time, and for solar-term entry times, we checked all 48 entries of the 24 solar terms for 2027 and 2028 against public data from the Korea Astronomy and Space Science Institute (KASI): every date matched, and the minutes differed by 0–1 minute. Iljin and year pillars were checked against a random sample of KASI's public lunar–Gregorian calendar. The resulting Four Pillars chart table is open for free in full, even on paid reading screens.
Can't I just leave the chosen day as it is?
Preparing for the day actually makes a bigger difference than choosing it. Date selection shifts the odds a little; it doesn't decide the outcome.
It's better to go into an ordinary day prepared than into a good day unprepared. The value of date selection comes from knowing about the day in advance.
So once you've chosen a date, there's just one thing to do — add it as an event. Whether it's a moving day or a contract day. What to do if you couldn't get the date you wanted is covered in When your moving date doesn't line up.
What Mutal Unnie can't do
I'll also be upfront about what it can't do when it comes to date selection.
- Date-selection methods from other schools, such as Nine Star Ki (gusonghak) or Qimen Dunjia (gimun dungap), aren't covered. Mutal Unnie works from Saju and iljin.
- Date selection for traditional rites such as reburials and burials is outside its scope. For those, it's right to see a specialist.
- It never says "do it on this day and it's sure to go well." The app's role ends at narrowing down candidates for you.
There's one thing you can do today — enter the date range for one date you need to decide. Whether it's a move or a contract, just seeing how few candidates remain makes the decision easier.
The day you need to decide — start by narrowing down candidates
Enter just a purpose and a date range to get candidates based on your Saju. The day you choose becomes an event as is.
Get the app for iPhone & AndroidFAQ
How do I choose a Saju app that does date selection?
Check five things: ① Does it ask for your date of birth? ② Can you choose a purpose? ③ Does it pick candidates within a date range? ④ Does it show its reasoning? ⑤ Does the chosen day carry over into your events? In practice, the apps most often lack ① and ⑤.
Does an app with only a Son-eomneun-nal calendar count as date selection?
That's a date lookup. Son-eomneun-nal are days whose lunar date ends in 9 or 0, so they're the same for everyone. It's a good starting point, but on its own it won't filter out days that clash with your zodiac animal.
Why do different apps give different "good day" results?
Because they look at different criteria. Results differ depending on whether an app looks only at Son-eomneun-nal, also checks zodiac clashes, or considers your personal chart and purpose as well. Whether the lunar calendar is calculated on a Korean basis also matters — between 1900 and 2050 there are 427 days where the verdict differs.
If I can't get a good day, should I postpone?
No need to postpone. Conditions you can't change come first, like your final-payment day or the wedding venue's availability, and date selection is about choosing the better option within those. If you only have one candidate, you can adjust the time of day or prepare a little more instead.