Daylight saving time and chart casting: that extra hour on the clock

Mainland China observed daylight saving time during designated summer periods from 1986 to 1991. For births recorded while it was in effect, subtract the extra hour before the subsequent chart-time conversion; otherwise the Hour Pillar may differ.

What is daylight saving time?

Daylight saving time advances clocks by one hour during part of the year to shift daily activity toward daylight, then reverses the change later. During that period, 8 am on the clock corresponds to 7 am standard time.

Birth certificates and hospital records generally show the clock time used then. For BaZi time conversion, first remove the extra hour if daylight saving was in effect.

The six years of daylight saving in mainland China

Mainland China observed daylight saving from 1986 through 1991. On the starting date, clocks jumped from 2 am to 3 am; on the ending date, they moved from 2 am back to 1 am. The yearly dates are listed below.

YearStart: advance one hourEnd: move clocks back
1986May 4September 14
1987April 12September 13
1988April 17September 11
1989April 16September 17
1990April 15September 16
1991April 14September 15

Mainland China stopped the practice from 1992. Taiwan, Hong Kong and Macao also observed daylight saving in earlier periods, on different schedules that must be checked separately.

An example

Consider a birth on July 10, 1988 recorded as 9:30 am. Daylight saving was in effect, so this corresponds to 8:30 am standard time. Before any further solar-time correction, 9:30 falls in Si hour (09:00–11:00), whereas 8:30 falls in Chen hour (07:00–09:00). This changes the Hour Pillar and may affect the traditional assessment of Day Master strength and Ten Gods relationships.

Births outside mainland China

Many places in Europe, North America and Australia observe daylight saving, but rules vary between countries and even within them. Most of Arizona, for example, does not observe it. In parts of the Southern Hemisphere that use it, daylight saving generally falls between about October and the following April, opposite to the Northern Hemisphere season.

For an overseas birth, simply applying today's time difference from Beijing is not enough. Resolve the birth city's historical time-zone and daylight-saving rules first, then perform the solar-time conversion.

Checklist

  • For births between April and September in 1986–1991, check the table above to determine whether daylight saving was in effect on the exact birth date.
  • For an overseas birth, enter the specific city rather than only the country: a country may span several time zones.
  • If two tools give different Hour Pillars, first check whether both handle daylight saving, then compare their solar-time conversions.

This page introduces traditional culture knowledge for reference only; it makes no predictions or guarantees about fate, health, relationships or wealth.

All 27 entries
Introduction and Chart SetupBaZi basics: Heavenly Stems, Earthly Branches and the Four Pillars

BaZi records a birth time using Heavenly Stems and Earthly Branches: two characters each for the year, month, day and hour. This introduction explains these eight characters, the sixty-pair cycle and the Four Pillars.

Introduction and Chart SetupSolar terms and the Month Pillar: why BaZi months do not begin on lunar day one

BaZi months change at the twelve jie boundaries: Li Chun starts the first month and Jing Zhe the second. Neither lunar day one nor the first day of a calendar month sets this boundary. Births near a solar-term transition need particular care.

Introduction and Chart SetupCan you calculate BaZi without knowing your birth hour?

Without the hour, the year, month and day still provide three pillars and six characters. They offer a Day Master and a partial elemental picture. Leave Hour Pillar matters uncertain rather than inventing a time.

Daylight saving time and chart casting: that extra hour on the clock · bazitao