節氣 · Lì Xià
Beginning of Summer立夏
The instant the sun reaches 45° of ecliptic longitude — the moment the month pillar's branch turns to 巳, and the calendar's turn to summer.
01概覽
Beginning of Summer (立夏, Lì Xià) is the seventh of the twenty-four solar terms and the fourth month-opener of the year, falling at the instant the sun reaches 45° of ecliptic longitude — usually 5 or 6 May. Like its counterpart Beginning of Spring, the name is a declaration rather than a description of conditions on the ground: 立 means "to set up" or "to establish", so the term marks summer being named rather than summer having fully arrived.
In the BaZi calendar it is a clean boundary: the point where 巳, the branch of the snake month, replaces 辰 in the month pillar. Everything that follows in the chart for a birth in this stretch of the year is read against 巳 rather than 辰.
02標記什麼
Astronomically, Beginning of Summer is a cross-quarter term — it sits at the midpoint between Spring Equinox and Summer Solstice, at 45° of ecliptic longitude, the same structural position Beginning of Spring, Beginning of Autumn and Beginning of Winter each hold relative to the equinox or solstice nearest them. In the agricultural calendar it traditionally marks the point where spring's growth gives way to summer's faster pace, with crops sown earlier in the year now filling out.
It opens the traditional "early summer" pairing with Grain Buds, mirroring the structure spring followed with Beginning of Spring and Rain Water.
03在八字命盤中
Beginning of Summer is a 節 — a month-opening term — so at that instant the month pillar's branch becomes 巳 (Sì). It is the fourth of the twelve month-branch changes over the course of a year, landing on a 節 like the other eleven.
Running this site's engine across 2026 confirms the specific timing: the month branch steps into 巳 on 2026-05-06, one of the twelve dates that year on which a pillar actually changes. A birth the day before still carries 辰 from Pure Brightness's month; a birth after this instant carries 巳.
Unlike Beginning of Spring, Beginning of Summer does not also move the year pillar — that is a distinction unique to the first month-opener of the year. Every other 節, this one included, changes the month pillar alone.