Ziwei dates and the 23:00 boundary
Which date should you enter, and why can a late-Zi setting change a chart? A worked example explains the app’s conventions.
Astrologram · Reviewed ·
Enter a Gregorian date
Astrologram’s Ziwei form takes a Gregorian birth date. iztro converts it for the lunar-calendar chart; the date field is not a lunar-date entry field. Enter the civil birth time as recorded. This calculation path does not apply an additional time-zone or true-solar-time correction.
If you only know a lunar date, confirm its Gregorian equivalent, including the year and whether it was a leap month, before entering it. Do not enter the same numbers as though they were a Gregorian date.
What happens at 23:00?
The app treats 23:00–23:59 as late Zi. The default “next day” convention advances the complete Gregorian date, then calculates with Zi hour. The optional “same day” convention keeps the entered date. At 00:00, use the actual date after midnight; do not manually advance it again.
This is a chosen chart convention. It is not evidence that one convention is universally correct for every Ziwei school. When comparing tools, match this setting before comparing stars or palaces.
A fictional New Year example
For a fictional input of 21 January 2023 at 23:30, female calculation sex, and the default leap-month adjustment, the installed engine gives the dates below. These demonstrate a boundary, not a personal forecast.
| Late-Zi setting | Calculation date | Lunar date |
|---|---|---|
| Next day (default) | 2023-01-22 | 2023, month 1, day 1 |
| Same day | 2023-01-21 | 2022, month 12, day 30 |
Leap months and year boundaries
The app’s default year boundary is lunar New Year, rather than the Start of Spring solar term. The example therefore crosses both a civil-date boundary and the chosen lunar-year boundary.
The default leap-month setting uses the numbered lunar month for days 1–15 and advances the month for later days. You can instead keep the original lunar month. This is separate from the late-Zi setting; match both when comparing charts.
Before comparing results
Check the calendar used for input, entered civil date and time, calculation sex, leap-month rule, and late-Zi rule. Astrologram shows its selected rules and calculation date in “About this chart.”
If the hour is unknown, the app uses noon. It cannot determine whether your actual birth was near a date boundary. Saved-profile selection generates immediately using the form’s current conventions; for a different convention, use the manual form and choose it before generating.