Compatibility can start without birth time
If one or both birth times are unknown, a compatibility reading can still compare year, month and day pillars. This can show broad rhythm, core self, relationship style and some Five Elements interaction.
Hour-pillar topics become less certain
The missing piece is the hour pillar. In relationship analysis, this may affect hidden drive, future direction, children-related themes and some long-term rhythm. A responsible reading should mark these parts as uncertain.
The day pillar remains important
The day pillar is still available if the birth date is known. It is central for close relationships because it relates to the self in intimate settings and how a person reacts when trust, safety or vulnerability is involved.
Five Elements can still show interaction
Even without birth time, the chart can still show whether one person's elements support, pressure or irritate the other person's pattern. The reading should avoid overclaiming details that depend on the missing hour.
Use it as a first comparison
Compatibility without birth time is useful for a first look, especially for communication style, pressure points and emotional rhythm. If the relationship decision is major, try to confirm birth time or keep the interpretation conservative.