FateTellCurrent calculation rules
- Date input
- Gregorian dates from 1900 to 2099
- Birth time
- Local clock time recorded at the birthplace, with historical UTC offsets and daylight saving time resolved from the selected time zone
- Year boundary
- The exact time of Li Chun (Beginning of Spring)
- Month boundary
- The exact times of the twelve Jie solar terms
- Day boundary
- The day always changes at 23:00
- True solar time
- Optional and off for a new entry; saved birth details retain their saved setting
- Luck cycle direction
- Yang-year males and Yin-year females move forward; Yin-year males and Yang-year females move backward. Yin or Yang is determined by the Year stem.
- Luck cycle start
- Calculated from the birth time’s position within the full interval between consecutive Jie terms, according to the cycle direction
- Ten Gods
- Determined by the element and Yin–Yang relationships to the natal Day stem
- Unknown birth time
- Use 12:00 noon at the birthplace, mark the hour as assumed, and skip true solar time correction
- Southern Hemisphere
- Enabling this option adjusts the Month pillar, as explained below
How birth time is handled
Use the birthplace’s local time and time zone
Enter the local clock time on the birth record and select the time zone used at the birthplace at that time. Keep these birthplace settings even if you now live in another country. The page may initially select your browser’s time zone, so check it before calculating.
Historical UTC offsets and daylight saving time follow the rules recorded in the IANA Time Zone Database. A location’s UTC offset can vary by year or season.
When daylight saving time ends, some clock times occur twice; the calculator always uses the first occurrence. When it begins, some clock times do not exist; the calculator converts them using the offset before the jump. If a birth record falls in either interval, verify the original record first.
How true solar time is calculated
When true solar time is enabled, the calculator adjusts the entered clock time using the birthplace longitude, the UTC offset on that date and the equation of time.
Correction in minutes = longitude × 4 − UTC offset in minutes + equation of time
East longitudes are positive and west longitudes negative; one degree corresponds to about 4 minutes. The equation of time is the difference between apparent and mean solar time, estimated using the method in NOAA’s solar calculation reference.
Correction requires a known birth time and a valid longitude. When it is off, longitude does not affect the time. When it is on, the corrected birth time is used for the Four Pillars and luck cycle start; the Year or Month pillar can also change if the correction crosses a Jie boundary. The solar term’s actual transition time stays the same.
How the pillars and luck cycles are calculated
Year and Month pillars change at solar term boundaries
The Year pillar changes at the exact time of Li Chun, not on January 1 or Lunar New Year’s Day. The Month pillar changes at each of the twelve Jie terms: Li Chun, Jing Zhe, Qing Ming, Li Xia, Mang Zhong, Xiao Shu, Li Qiu, Bai Lu, Han Lu, Li Dong, Da Xue and Xiao Han.
Solar term data comes from the lunar-typescript calendar library. Birth and transition times are converted to a shared time basis before comparison. The Month stem is derived from the Year stem using the Five Tigers rule. Near a solar term boundary, compare the exact times rather than the dates alone.
The Day pillar changes at 23:00
The calculator always changes the day at 23:00. At the start of the Zi hour, it uses the next day’s Day pillar and derives the Hour stem from that day. With true solar time enabled, the corrected local time determines whether 23:00 has been crossed.
The Day stem is the Day Master, so a change in the Day pillar also affects the Ten Gods. The Hour stem is derived from the Day stem using the Five Rats rule. For births from 23:00 to 23:59, check how both the Day pillar and Hour stem are chosen when comparing tools.
Luck cycle direction and start time are separate calculations
Luck cycles move forward for Yang-year males and Yin-year females, and backward for Yin-year males and Yang-year females. Yin and Yang come from the Year stem: Jia 甲, Bing 丙, Wu 戊, Geng 庚 and Ren 壬 are Yang; Yi 乙, Ding 丁, Ji 己, Xin 辛 and Gui 癸 are Yin.
The starting age is calculated from the birth time’s position within the full interval between consecutive Jie terms. Forward cycles use the time from birth to the next Jie; backward cycles use the time from the previous Jie to birth:
Forward starting age = time from birth to next Jie ÷ full interval between Jie terms × 10 years
Backward starting age = time from previous Jie to birth ÷ full interval between Jie terms × 10 years
The conversion uses 365.2422 days per year, truncating the displayed years, months and days at each step. Tools that use another convention, such as “three days equal one year,” may give a different start even when the Four Pillars match.
Ten Gods are relative to the Day Master
The Ten Gods depend on both the element and Yin–Yang relationships between each stem and the natal Day stem. For example, Gui Water is Nurturer to Jia Wood and Sage to Yi Wood. Heavenly Stems and Hidden Stems are listed separately; Ten Gods in 10-Year Luck, Annual and Monthly pillars also use the natal Day Master as their reference.
The simplified element count covers only the four Heavenly Stems and the main element of each of the four Earthly Branches: 8 entries in total. It does not weight Hidden Stems or directly assess element strength. For definitions, see the guides to the Day Master, Five Elements and Ten Gods.
The Southern Hemisphere option adjusts the Month pillar
When the Southern Hemisphere option is enabled, the Month branch moves to its opposite position and the Month stem is recalculated from the original Year stem using the Five Tigers rule. The stems and branches of luck cycles, Monthly pillars and related palaces are adjusted accordingly.
This option alone does not change the Year, Day or Hour pillar, or the actual solar term transition time. It is a calculation choice offered by FateTell; not every tradition uses this Southern Hemisphere rule.
An unknown birth time is treated as noon
If the birth time is unknown, the calculator uses 12:00 noon at the birthplace for the Four Pillars and luck cycle start. It labels the hour as assumed and skips true solar time correction. Recalculate if the birth time becomes available later.
The assumed Hour pillar still contributes to element counts, luck cycle timing and related palaces. On a solar term transition date, the Year or Month pillar calculated at noon can also differ from the one at the actual birth time. This chart is based on a noon assumption and is not a complete result with a confirmed birth time.
Calculation examples
All examples use fictional birth details for comparing calculations. Unless stated otherwise, select male, Northern Hemisphere, known birth time and true solar time off. The day boundary is always 23:00.
For the China examples, select Asia/Shanghai (Beijing time) and longitude 116.4074° E; this is called Shanghai time below. For New York, select America/New_York and longitude 74.006° W. A time zone name does not identify the birth city; use the longitude specified in each example.
Basic example: pillars, elements and luck cycle start
Enter January 1, 2000 at 12:00, Shanghai time.
- Four Pillars
- Year 己卯, Month 丙子, Day 戊午, Hour 戊午
- Day Master
- Wu Earth (戊)
- Element counts
- Wood 1, Fire 3, Earth 3, Metal 0, Water 1
- Luck cycle direction
- Backward
- Starting age
- 8 years, 4 months, 4 days
- First luck cycle begins
- May 6, 2008 at 04:26:24 (Shanghai time)
Seconds indicate only the precision of the displayed calculation, not an equal level of accuracy in the birth record or conversion method.
1. At the Zi hour boundary, both Day and Hour pillars change
Keep the date and time zone from the basic example; change only the birth time.
| Entered time | Day pillar | Hour pillar |
|---|---|---|
| 22:59 | 戊午 | 癸亥 |
| 23:00 | 己未 | 甲子 |
2. Year and Month pillars change at Li Chun
Enter February 4, 2024, Shanghai time, with true solar time off.
| Entered time | Year pillar | Month pillar |
|---|---|---|
| 16:20 | 癸卯 | 乙丑 |
| 16:30 | 甲辰 | 丙寅 |
3. True solar time crosses the day boundary
Enter January 2, 2000 at 00:05, Shanghai time, and change the longitude to 90° E.
| True solar time | Time used for the chart | Day / Hour pillar |
|---|---|---|
| Off | Jan 2, 00:05:00 | 己未 / 甲子 |
| On | Jan 1, 22:02:01 | 戊午 / 癸亥 |
4. Historical daylight saving time affects solar correction
Enter July 1, 1988 at 09:00, Shanghai time, longitude 116.4074° E. The UTC offset on that date is UTC+09:00.
| True solar time | Time used for the chart | Hour pillar |
|---|---|---|
| Off | 09:00:00 | 乙巳 |
| On | 07:42:04 | 甲辰 |
Enter the clock time on the birth record directly; do not subtract the daylight saving hour yourself.
5. Repeated or missing times at daylight saving transitions
Use New York time with true solar time off. The two cases are converted as follows:
| Entered time | Offset used | Equivalent UTC time |
|---|---|---|
| Nov 3, 2024, 01:30 (repeated) | UTC−04:00, first occurrence | Nov 3, 05:30 |
| Mar 10, 2024, 02:30 (missing) | UTC−05:00, before the jump | Mar 10, 07:30 |
A conversion result does not make a nonexistent clock time a real birth time. The original record still needs to be checked.
6. The same solar term boundary in different time zones
Enter February 3, 2026, New York time, with true solar time off.
| Entered time | Year pillar | Month pillar |
|---|---|---|
| 15:01 | 乙巳 | 己丑 |
| 15:03 | 丙午 | 庚寅 |
February 3 at 15:03 in New York and February 4 at 04:03 in Shanghai are the same instant. With Northern Hemisphere selected and true solar time off, their Year and Month pillars match. Day and Hour pillars use each location’s local time and may differ. For your own chart, enter the actual birthplace details.
7. An unknown birth time can affect more than the Hour pillar
Enter February 4, 2024, Shanghai time, and select unknown birth time. Using noon, the calculator produces Year 癸卯, Month 乙丑, Day 戊戌 and Hour 戊午, with the Hour pillar marked as assumed.
If the birth time is later confirmed as 16:30, recalculating gives Year 甲辰 and Month 丙寅. On a solar term transition date, even the Year and Month pillars from a noon assumption cannot be treated as certain.
8. One stem has different Ten Gods for different Day Masters
| Natal Day Master | Compared stem | Ten Gods |
|---|---|---|
| Jia Wood (甲) | Gui Water (癸) | Nurturer |
| Yi Wood (乙) | Gui Water (癸) | Sage |
Changes to the calculation method
These changes can affect chart results. Use this record when comparing older and newer charts.
September 2026
Aligned solar term comparisons and luck cycle start calculations across time zones; included true solar time in Year and Month pillar calculations; fixed the day boundary at 23:00; and specified how repeated and missing daylight saving times are handled. These changes can affect Year and Month pillars near solar term boundaries, Day pillars near the Zi hour, and luck cycle starting times.
January 2026
Standardized unknown birth times to noon for both the Four Pillars and luck cycle start, marked the hour as assumed, and skipped true solar time correction. This affects the assumed Hour pillar, element counts, luck cycle start and, on solar term transition dates, the Year or Month pillar.
September 2025
Added the Southern Hemisphere option: move the Month branch to its opposite position and recalculate the Month stem. Enabling it affects the Month pillar, luck cycle stems and branches, and related fields.
When comparing older screenshots, retain not only the birth details but also the time zone, longitude, true solar time setting, hemisphere and whether an assumed birth time was used.
What to check when two charts differ
- Start with the input. Check the Gregorian date, birthplace and local clock time. If the original record uses the lunar calendar, verify the conversion and whether it is a leap month.
- Check the time settings. Confirm the time zone, historical daylight saving time, longitude and true solar time setting.
- Look for nearby boundaries. Pay attention to Li Chun, monthly Jie transitions and the 23:00 day boundary. Check how the Hour stem is derived as well.
- Compare pillars and luck cycles separately. Matching Four Pillars with different luck cycle start times may reflect different conversion methods. For cycle direction, also check gender and the Yin or Yang of the Year stem.
- Finally, check the Ten Gods reference. Confirm the Day Master first, then compare the element and Yin–Yang relationships of the other stems.
Differences can come from settings, source records or calculation conventions, as well as implementation errors. If results still differ with the same input and rules, examine the individual calculation steps.
What the chart can tell you
The free calculator displays the Four Pillars, Ten Gods and luck cycle fields calculated under these rules. Element counts are not measures of strength and do not directly determine Supporting Qi or good or bad fortune. The calculated chart does not, by itself, establish the validity of predictions about real events.
Keep the uncertainty in mind when the birth time is unknown or near a boundary, and check again when more information becomes available.