You can find lots of countdown tickers here:
Arranged into the following categories (many of them several pages each):
Valentines, Hearts, Love, Birthday, Video, Fun, Pregnancy, Anniversary, Wedding, Engagement, Graduation, Funny, Smiles, USA, Aquarium, Cats, Dogs, Autumn, Canada Day, Girly, Retirement, Soldier Returning Home, Spring, Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, Pisces, Flowers, Nature, Cinco De Mayo, Mother’s Day, Labor Day, Back To School, Memorial Day, Father’s Day, Fourth Of July, St. Patrick’s Day, Cool, Gemstones, Cute, Easter, Halloween, Thanksgiving, Christmas, New Year.
All the tickers are resizable. Some of them display up to 3-digit day numbers only.
If you find one you like, click “GET CODE”, copy the code and paste it in a simple text file. It will look like this:
Get the widget name and the dimensions (the bits I have highlighted in blue in the example) and create a working shortcode using this model:
(Replace NAME with the actual widget name, Y,M,D,W,H with the right numbers, EVENT with your event.)
Paste shortcode into text widget or html post/page editor.
Caution: may not display correctly in Explorer – use at your own risk (till Explorer learns to behave, or till users learn not to use Explorer).
General background: The gigya shortcode 3 – widgets.
Related post: generic countdown timers