In the month of April, once the 17th April is reached, users can no longer request leave for March and any month prior to that but they can request from 1st to 17th April and as well as for the future dates too.
If it’s 10th of April when the 17th has not yet been reached, employees can still request leave only for the previous month (i.e., March) and future months(i.e., April, May, June.....) but not prior to that months (i.e., February, January, .....).
Successfactors - Employee Central Time Off
Create a Take Rule as below and assign to the particular time Type:
Time off Take Rule Past Leave Restrict Previous Months , KBA , LOD-SF-EC-TIM , Time-Off , How To