Eclipses come in pairs about a fortnight apart, and modern practice calls the gap between them a portal or a corridor and treats it as a single stretch of unstable time.

The fortnight is real and follows from geometry: if the Moon is near a node at new moon it will be near the opposite node at full. The tradition's contribution is the mood — do not sign anything, do not cut your hair, wait. It is the largest scheduling decision most practitioners make, and it happens four to six times a year.