Daylight Saving Time (夏令時) in Bazi Calculation
Learn how historical daylight-saving rules affect Bazi birth times, skipped and repeated clock times, and the order used before solar-time correction.
Overview
Daylight Saving Time (夏令時) is a civil-clock offset adopted by a jurisdiction for a stated period; it is not a Bazi symbol. A reliable chart must resolve the named place and historical date through a time-zone rule set, including skipped spring times and repeated autumn times, before applying longitude correction or pillar boundaries. A modern “UTC+8” assumption can be wrong for historical births. OpenFate treats the resolved instant and any ambiguity as calculation provenance rather than interpretive evidence.
At a glance
- Data type
- Historical civil-time offset rule
- Required inputs
- Location, local date and local clock time
- Spring transition
- Some local times do not exist
- Autumn transition
- Some local times occur twice
- Processing order
- Resolve offset before solar and pillar rules
- Boundary
- Not a symbolic or predictive factor
DST changes the civil-clock label attached to an instant
Governments have changed daylight-saving dates and offsets across years. The same city can therefore use different UTC offsets on two historical dates.
A birth certificate records local civil time, not necessarily standard time. The applicable historical rule must be recovered before converting the instant.
- Use an IANA location identifier when available.
- Do not infer historical offset from today’s clock.
Clock changes can create missing or duplicated local times
When clocks move forward, an interval can be skipped and a written local time may never have occurred. When clocks move back, one local time can correspond to two distinct instants.
The system should reject or flag a nonexistent time and request disambiguation for a repeated time. Guessing an offset can change the hour or day pillar.
- Validate gaps instead of auto-correcting silently.
- Preserve the chosen occurrence for a repeated time.
OpenFate resolves civil time before true solar time and pillars
The calculation pipeline maps place and date to the historical offset, creates a definite instant, then applies any selected true-solar correction and day-boundary doctrine.
Historical regression cases for China and Taiwan protect this order. An explicit numeric offset remains provenance and should not be presented as equivalent to a location rule without disclosure.
- Keep civil offset and solar correction as separate steps.
- Store the resolved zone rule with the result.
DST is a calculation correction, not a destiny interpretation
Daylight-saving status can change computed pillars near a boundary, but it does not add a star, element, score or personality meaning.
If the place, date or repeated-time occurrence is unknown, the chart should disclose uncertainty. It should not invent precision or make medical, legal, financial or relationship claims from the clock rule.
- Explain any pillar sensitivity caused by the offset.
- Do not turn an administrative rule into symbolism.
Sources and editorial basis
- IANA Time Zone DatabaseIANA Time Zone Database：保存各地歷史 UTC 偏移與日光節約時間規則，包含缺口與重複時刻所需的轉換資料The maintained reference for historical local-time rules, UTC offsets, and daylight-saving transitions by location.
- 《御定星曆考原》卷一《御定星曆考原》卷一提供干支與曆法時刻配屬的歷史語境；現代民用時制校正須在干支界線之前完成A historical source for stem and branch Yin-Yang, Five Phase, direction, seasonal, and calendrical correspondences.
- OpenFate Editorial Methodology產品 DST civil correction 測試覆蓋中國 1986–1991、臺灣 1946–1961、午夜換日及農曆一致性；日光節約時間不作神煞、五行或吉凶輸入OpenFate separates deterministic chart calculation, traditional interpretation, and modern editorial explanation.