Over the year, Federal holidays are unevenly clumped giving some months two holidays and then months on end without any. Several of these holidays can be changed to spread them out better over the calendar. Veterans would probably prefer to be celebrated during a warm May Day BBQ rather than a cold November one day spent getting ready for thanksgiving.
Also, observe federal holidays on either Friday or Monday for long weekends (except Thanksgiving and Christmas).
Lastly, as there aren't enough current holidays for a once-a-month holiday, establish National Awesome Day in April to celebrate how awesome America is and how awesome the end of winter is.