Symptoms
As an administrator, am not able to change the out of office settings for a user and getting an exception "the until date can not be smaller than the current date".
Diagnoses
Check entries in the [Server].[ActionerShare] table on the k2 sql database
Resolution
Make a backup copy of the k2 database then setting all row with column of StartDate and EndDate colum to be "NULL".
Then try adding the out of office and resolve the issue.