The date [day,week,month,year] x1=d1=k1 is recurrence/repetition of the date [day,week,month,year] of the first event x2=d2, for the x3=k3'rd time, in system x3.
detri zei krefu. krefu2 corresponds to the date of the first event, but the place is omitted for simplicity. x4 may indicate the system of recurrence: a day of the week/month; a day/month of the year (anniversary); a year of the century etc. ex.) li renopavo pi'e pano pi'e re detke'u lo nu la gandis noi banli cu jbena kei li pavomu lo pa nanca be fi la gregoris (October 2 of 2014 is Mahatma Gandhi's 145th birthday counted by year of Gregorian calendar.)