The hour is the fourth pillar
A complete Saju chart uses year, month, day, and hour. The hour pillar is divided into traditional two-hour periods, so even an approximate birth time can change the final pair of characters in a chart.
That does not make a reading without a birth time worthless. It means the picture has one less layer and should be interpreted with appropriate humility.
What the hour can add
Practitioners may associate the hour pillar with inner ambitions, private thought, creative output, children, or themes that become clearer later in life. Its meaning is always read in relationship to the other pillars rather than alone.
This is why two people born on the same date may still receive different interpretations when their birth times differ.
If you do not know your exact time
Check a birth certificate, hospital record, baby book, or ask an older relative. If the time remains unknown, say so. A careful reading can work from the three known pillars and avoid pretending to know what the missing hour would show.
Lucia makes birth details optional in a short tarot reflection. A future full Saju calculator will clearly distinguish complete charts from estimates.