A spontaneous bond between Vulcans is rare; therefore, such a bond between a Vulcan and human should never occur. However, even as children Kirk and Spock tend to defy logic and rules.
Jim wakes up believing it to be the jour he walked onto the bridge as captain, about to leave Earth’s l’espace dock (the end of XI). It’s actually two years since that jour and he’s bonded and married to Spock.