public void setModificationDate(Date modificationDate) {
        this.modificationDate = modificationDate;
    }
Sets the last date when the room's configuration was modified. If the room's configuration
was never modified then the initial value will be the same as the creation date.

@param modificationDate the last date when the room's configuration was modified (cannot be {@code null}).
xmppserver/src/main/java/org/jivesoftware/openfire/muc/MUCRoom.java