When it comes to finding synonyms for the phrase "sad day," there are many options available to express the emotions that come with such an event. You could replace "sad" with "tragic," "devastating," "heartbreaking," or "mournful." If you want to emphasize the pain and suffering involved, "grieving" or "mourning" might be more appropriate. Similarly, "bleak," "dismal," and "dreary" convey a sense of emptiness and loss. On the other hand, if you're looking for a more gentle way to speak about sadness, "sorrowful," "melancholy," or "wistful" can convey a sense of nostalgia or longing. Whatever word you choose, it's important to use language that accurately reflects your emotions.